I would not call a post-migration traffic dip a mystery when redirects, templates, and internal links are still messy. Some drop is normal. A long hangover usually means something technical or structural is still broken.
Week one vs week six
Early volatility happens. Crawlers relearn. Rankings shuffle.
If money pages are still down after redirects are supposedly done, you have work.
I would audit in this order
Redirect map: every old URL with traffic should resolve cleanly.
Canonicals and duplicates: did migration create twins?
Internal links: did nav and body links still point to old paths?
Templates: did title tags and main content blocks change on key URLs?
Sitemaps and Search Console: are the right properties reporting errors?
Content changes matter too
If you rewrote top pages "for SEO" during migration, you may have traded familiarity for cleverness.
Compare old and new HTML on winners.
Do not spam new posts to fix a hangover
Publishing fresh blog posts while service pages 404 is busywork.
Fix the foundation. Then expand.
Migration hangover is mitigated by boring discipline: redirects tested, templates stable, and patience paired with weekly checks on URLs that actually pay you.
