Almost every migration shows a dip somewhere in the first three weeks. The question is which dip is normal and which one is a bug.
Crawl volume and impressions wobble while Google reprocesses your URLs. That is expected. What is not expected is a permanent loss on your top twenty landing pages. That always traces back to a missing redirect, a changed page structure or lost structured data.
Conversion often moves in the other direction. A faster storefront and a cleaner checkout usually lift conversion within the first month, which hides a ranking problem in the revenue number.
This is why we monitor page level, not site level. SEO Guard compares your top pages before and after, so you know within days which page needs attention instead of guessing after a quarter.