This is a classic and very common scenario in Google Ads, and it's frustrating but fixable. You've essentially "corrected" the data Google's algorithm was learning from, and now it needs to adjust.
Here's what's happening and what you should do:
What Happened:
The Algorithm Learned Bad Data: For the past two months, your Google Ads campaign (especially if it was using Smart Bidding strategies like Target CPA or Maximize Conversions) was optimizing based on inflated conversion numbers. It thought it was hitting your $6 CPA target because it was seeing double the conversions.
The Learning Phase Re-Adjusted: When you removed the duplicate code, you essentially changed the "truth" for the algorithm. It's now in a sort of "re-learning" or "adjustment" phase. It's realizing that the signals it was getting were inaccurate, and it's trying to find actual conversions at your target CPA with the correct, lower count.
Performance Drop is Expected: A sudden drop in CPA performance, increased spend for fewer conversions, or even a temporary dip in delivery is normal and expected after such a significant change in conversion tracking. The system now knows your $6 CPA was based on a false premise.
What You Should Do:
1. Let it go and correct itself (with minor adjustments):
This is generally the recommended approach for a campaign that's been running for 2 months. The campaign has a significant amount of other historical data (keyword performance, ad performance, audience signals) that is still valuable.
The algorithm needs time to re-optimize. It's already in the process of learning the new, correct conversion rate.
How long to wait? Give it at least another 7-14 days with the correct tracking in place. Smart Bidding strategies need enough new, accurate conversion data to recalibrate.
Adjust your CPA target: Your actual CPA was probably much higher than $6 previously, you just didn't see it. The current higher CPA is likely closer to your true cost. You need to adjust your target CPA upwards to a more realistic value based on your current (correct) data. If you were truly getting conversions at $6, and now it's $12 with the correct tracking, then your old campaigns were actually performing at $12.
Start by setting your Target CPA to what you're actually seeing now (e.g., if it's currently $15, set it to $15).
Once it stabilizes there, you can gradually try to bring it down by 10-15% every few days/week, if the volume allows.
2. Do NOT copy the campaign and start from scratch:
Why not: Starting from scratch would mean throwing away all the valuable historical data (impressions, clicks, quality score, auction insights, etc.) that your existing 2-month-old campaign has accumulated. It would force a complete reset of the learning phase, which would likely lead to even worse performance and higher CPAs initially as the new campaign learns from scratch with no historical context.
The old campaign, despite the tracking hiccup, still has a performance history that the algorithm values. It just needs to re-learn the conversion rate within that existing framework.
Key Takeaways & Actions:
Patience: Smart Bidding needs data. Give it 1-2 weeks.
Adjust CPA Target: This is critical. Don't expect to hit $6 overnight if your true CPA was higher. Incrementally increase your target CPA to match what the campaign is actually delivering now with accurate tracking.
Monitor: Watch your actual conversion numbers, quality scores, impression share, and bid strategy status (in the "Bid Strategy" column) daily. Look for "Learning" or "Learning limited" messages.
Quality Data is King: You've fixed a major tracking issue. While painful in the short term, this correct data is essential for long-term sustainable optimization.
It's a tough pill to swallow to see performance dip, but you've done the right thing by correcting the tracking. The system just needs to catch up to the new reality.