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.