I've been troubleshooting similiar issues and I found this post that windows search is corrupting the user edb on server 2019 because the edb is moved to the appdata\roaming folder which is abruptly removed while the indexer is still accessing it. Maybe this is causing your issues too. Their solution was to create a scheduled task to restart the Windows search service on a user logout event ID.
https://jkindon.com/2020/03/15/windows-search-in-server-2019-and-multi-session-windows-10/