Meta Ads Performance Volatility: Why ROAS and CPA Are Fluctuating in 2026

In September and October 2026, Facebook and Instagram advertising specialists began actively discussing unstable Meta Ads performance. Professional communities have seen reports of sudden changes in conversion costs, declining ROAS, and substantial differences in sales volumes from one day to the next.

A notable characteristic of these complaints is that results can change even when advertisers make no adjustments to budgets, audiences, or ads.

Some marketers associate these developments with Meta's evolving algorithms, including Andromeda. Others point to stronger advertising competition ahead of the fourth quarter, seasonal changes in demand, and declining effectiveness of familiar ad creatives.

However, it is important to distinguish advertiser observations from confirmed platform changes. Meta has not announced a single technical update during August through October 2026 that can be considered the proven cause of all the reported fluctuations.

What Advertisers Are Saying About Meta Ads Performance Volatility

The topic is being discussed most actively on Reddit, particularly in the r/FacebookAds community, where advertisers and performance marketing specialists share their campaign results.

In September, reports emerged of noticeable declines in ROAS following relatively successful summer months.

In one discussion, an advertiser explained that their campaigns had consistently generated ROAS above 5 in July and August, but performance deteriorated in mid-September and results became less predictable. As a result, the company temporarily decided against increasing its budget ahead of the Black Friday season.

In October, users continued reporting similar problems. One advertiser with a daily budget of approximately $150 described a situation in which the same campaign could generate eight sales on one day and none the next.

Other participants reported rising CPA, fluctuating CPM, and situations where a new campaign performed well during its first two days before its effectiveness dropped sharply.

At the same time, feedback is not uniform. The same discussions include advertisers who continue to run profitable campaigns and maintain stable ROAS.

These posts help identify common questions and problems, but they do not provide sufficient grounds to conclude that Meta Ads performance has deteriorated for most advertisers.

Why Meta Ads Results Can Change Sharply Without Changes to Campaign Settings

Meta Ads operates as an auction-based advertising system. The cost and outcome of each impression depend not only on campaign settings, but also on competition among advertisers, user behavior, and algorithmic predictions.

Even when a campaign remains unchanged, the conditions under which it operates are constantly changing.

Changes in Competition and Advertising Costs

The cost of advertising on Facebook and Instagram depends on demand for advertising inventory.

Ahead of the fourth quarter, many online retailers begin increasing their budgets in preparation for seasonal promotions and holiday shopping.

When more advertisers compete for the attention of the same audience, impression costs can rise.

For example, with CTR remaining unchanged, an increase in CPM from $10 to $13 raises the cost of acquiring traffic by approximately 30%.

Even a slight decline in Conversion Rate can then push CPA higher.

As a result, advertisers may see a substantial deterioration in their cost per sale even though they have not changed their audiences or ads.

Limited Data and Random Fluctuations

Daily metrics in smaller advertising campaigns are particularly sensitive to random fluctuations.

Suppose an online retailer generates an average of five purchases per day.

One day without any sales followed by a day with eight orders may look like a serious failure in the advertising system. However, when conversion volumes are low, a significant share of such fluctuations can occur naturally.

Under these conditions, evaluating advertising based on a single day's results leads to poor decisions. Advertisers may pause ads that are still capable of achieving their target CPA or increase budgets following an unusually successful day.

Therefore, analysis should consider not only average performance metrics, but also the volume of accumulated data.

Changes in Consumer Behavior

Advertising results also depend on users' willingness to make purchases.

In September and October, some consumers may postpone orders while waiting for seasonal promotions, including Black Friday.

For online retailers, this can lead to lower Conversion Rates even when CPM and CTR remain stable.

In other categories, demand may accelerate instead.

Therefore, deteriorating campaign results are not always related to algorithmic problems. Sometimes, the effectiveness of the offer itself changes in the market.

Creative Fatigue

Even a successful ad can become less effective over time.

Users repeatedly encounter familiar images and videos, interact with them less frequently, and the cost of acquiring customers gradually increases.

This is particularly important in Meta Ads because creative assets do more than attract attention. They also contribute to the automated assessment of an ad's relevance to specific users.

When a campaign uses several nearly identical creatives, it becomes more difficult for the algorithm to identify different groups of interested buyers.

Therefore, creative diversity becomes more important than simply increasing the number of ads.

How Andromeda Affects Meta Ads Performance

In discussions about advertising volatility, advertisers frequently mention Andromeda, a machine learning system Meta introduced in December 2024.

Andromeda is responsible for the initial stage of ad retrieval.

Before determining which ad to show a user, Meta must select a relatively small number of suitable candidates from an enormous pool of available ads.

Andromeda performs this task by analyzing creative characteristics and user signals, then retrieving ads for subsequent ranking stages.

Thanks to its new architecture, Meta can account for more complex relationships between user interests and advertising offers while processing a significantly larger variety of creative assets.

In March 2026, the company also introduced the Meta Adaptive Ranking Model, an evolution of its ranking system that uses more sophisticated models to evaluate ad candidates.

As a result, the advertising platform is gradually moving toward a model in which algorithms play an increasingly important role in audience selection and impression delivery.

For advertisers, this means that manually defining highly granular audiences is gradually becoming less important relative to the quality of conversion signals, the appeal of the offer, and the diversity of advertising creatives.

However, it would be incorrect to claim that Andromeda specifically caused the performance instability observed in fall 2026.

The system was introduced considerably earlier, and Meta has not confirmed a direct connection between any specific Andromeda update and advertiser complaints in September and October.

How to Identify the Cause of Declining ROAS or Rising CPA

Before changing an advertising campaign, it is useful to determine which metric is responsible for the deterioration in performance.

For online retailers, a basic diagnosis can be conducted using three metrics: CPM, CTR, and Conversion Rate.

What Changed	Possible Cause	What to Check
CPM increased, while CTR and CR remained stable	Higher advertising inventory costs	Competition, seasonality, impression distribution
CTR declined, while CPM remained stable	Reduced ad appeal	Creatives, offers, ad frequency
CTR remained stable, while CR declined	Post-click conversion problems	Website, pricing, product availability, checkout
CPM and CTR remained stable, while CPA fluctuated	Low conversion volume or attribution delays	Data volume, attribution windows, actual orders
CPA increased alongside Frequency	Potential audience or creative fatigue	Reach, repeated impressions, CTR trends
ROAS declined, while CPA remained stable	Changes in average order value	AOV, product assortment, discounts, sales mix

This approach helps distinguish advertising auction problems from changes in an online retailer's operations.

For example, if CPM increases by 20% but Conversion Rate rises by 30%, the resulting CPA may actually improve.

Therefore, rising impression costs do not necessarily indicate deteriorating advertising efficiency.

What Advertisers Should Do When Performance Becomes Unstable

Do Not Change Campaigns After Every Bad Day

One of the most common mistakes is constantly adjusting budgets, ads, and audiences in response to short-term fluctuations.

Significant changes can affect learning and impression distribution.

This does not mean unprofitable campaigns should continue running regardless of performance. However, decisions should be based on sufficient data and predefined criteria.

For example, an advertiser can analyze performance over the past 7 or 14 days while also considering a longer-term trend.

For smaller campaigns with infrequent conversions, a longer observation period may be necessary.

Verify Results Against Store or CRM Data

Meta Ads reports conversions according to its own attribution rules.

Because of event transmission delays and differences between platform attribution and actual orders, daily metrics may not fully match online store data.

Therefore, advertising reports should be compared with actual sales, revenue, and order quality.

For B2B advertisers, it is particularly important to evaluate not only submitted forms, but also the number of qualified leads.

Refresh Advertising Creatives Regularly

If CTR gradually declines, Frequency increases, and results deteriorate over several weeks, this may indicate creative fatigue.

In that case, advertisers should test not only new images of the same product, but also different approaches to promoting it.

For example, a clothing brand can use separate ads demonstrating garment fit, fabric quality, production characteristics, and ways to style the item with other pieces.

Different advertising messages make it possible to reach shoppers with different motivations and preferences.

Avoid Unnecessarily Complicated Account Structures

A large number of campaigns and ad sets can cause budgets and conversion data to become excessively fragmented.

For smaller advertisers, it is particularly important to avoid situations in which each ad set receives too few events for stable optimization.

Simplifying the structure can help the algorithm use available data more effectively, although the optimal number of campaigns depends on the product assortment, geography, budget, and business objectives.

Run Experiments Instead of Changing Everything at Once

When performance deteriorates, advertisers may be tempted to change audiences, budgets, creatives, and optimization strategies simultaneously.

However, after making all these changes, it becomes practically impossible to determine which adjustment affected the results.

It is much more useful to test individual hypotheses sequentially.

For example, advertisers can test a new set of creative assets while keeping other conditions unchanged, or compare two budget management strategies.

With sufficient data, Meta Experiments allows advertisers to organize A/B tests and evaluate differences between alternatives.

What Will Happen to Meta Ads Performance in Q4 2026?

Fall is traditionally a period of increased competition for advertising impressions on Facebook and Instagram.

Online retailers prepare for Black Friday, Cyber Monday, and Christmas shopping, potentially increasing pressure on advertising inventory costs.

However, current discussions do not support the conclusion that Meta Ads algorithms have systematically deteriorated.

Some advertisers report substantial increases in CPA and declines in ROAS. Others continue to generate profitable sales even in a more competitive environment.

These differences may be explained by product assortment, geographic markets, budgets, conversion data quality, and the competitiveness of advertising offers.

Therefore, businesses should focus less on predicting the direction of algorithm changes and more on defining acceptable customer acquisition costs, ensuring accurate conversion measurement, and preparing several independent advertising hypotheses.

Affect's Takeaway

Discussions about Meta Ads performance instability in fall 2026 reflect a genuine challenge for advertisers: the results of automated campaigns are becoming more difficult to predict over short periods.

However, sharp fluctuations in ROAS and CPA are not always caused by technical changes to the advertising platform.

Overall performance is affected simultaneously by advertising competition, consumer demand, ad quality, website conversion rates, and the volume of statistical data.

The development of Andromeda and Meta's other algorithms increases the importance of automation, but does not eliminate the need for professional advertising management.

Affect recommends that advertisers focus on three areas: conversion data quality, systematic testing of diverse advertising creatives, and performance analysis over a sufficiently long period.

The main objective of performance marketing is not to achieve identical ROAS every day, but to maintain sustainable advertising profitability over an extended period.

Sources

1. Meta Engineering, December 2, 2024: Meta Andromeda: Supercharging Advantage+ Automation. Meta Engineering
2. Meta Engineering, March 31, 2026: Meta Adaptive Ranking Model. Meta Engineering
3. Search Engine Land, January 28, 2026: Inside Meta's AI-Driven Advertising System: How Andromeda and GEM Work Together. Search Engine Land
4. Reddit r/FacebookAds, September 20, 2026: Meta Volatility in September. Reddit Discussion
5. Reddit r/FacebookAds, September 28, 2026: Meta Ads Performance Dropped Since Mid-September. Reddit Discussion
6. Reddit r/FacebookAds, October 9, 2026: Really Strange, Volatile Performance. Reddit Discussion
7. Reddit r/FacebookAds, October 14, 2026: Is Anyone Still Seeing Profitable Returns With Meta Ads? Reddit Discussion
8. Reddit r/FacebookAds, October 8, 2026: Any Improvements on Performance Today? Reddit Discussion