We experienced a drop in site tracking early in October. At the same time UA stopped recording.
After way too much time troubleshooting, this was the problem:
<script>dataLayer = [{'pageCategory': '2', 'pageCategoryName': 'Sub City Page'}];</script>
Our legacy page category tracking was stepping on the pageview from being sent from those pages from GA4. This was not an issue for the first 15 months of GA4's tracking. So Google changed something.
If you are experiencing similar issues, I would look for legacy dataLayers.
Joe
