Check it, before you wreck it!
Yep. I’m corny. But it may be worth taking a glance at your GA4 settings. One thing I recently noticed was the new (to me, at least) Reporting Identity setting with the ‘Blended’ option selected by default. Seems like this is a good idea as cookies are on the chopping block next year and Chrome and continue to be less and less reliable identifiers as more and more privacy regulations are in place.