I have set up user_id tracking on an SPA (Single Page Application). It works fine, but the problem is that the user_id is only assigned to custom events in the raw GA4 BigQuery table, and not to other events like session_start, first_visit, etc.

I made sure that the GA4 tag fires before any other event by setting the Tag Firing Priority to 100, while the others have the default value of 0. Additionally, GA4 is triggered on the page_view event.

Do you have any idea why this is happening, and how I can ensure the user_id is assigned to all events, including session_start and first_visit?

Thank you for your help!