Is your data base split? See Split Your Database

Are all the users opening the same Accdb or Accde folder on your shred folder? if So, that is a big No No.

Do you have the latest updates?  Reason I ask is a recent update has a tendency at least for me to not close correctly.  Leaves a lock behind.  And per Windows task manager it's still running.  Make sure you have no instances of Access running and delete the locks.

If these things are happening roll the update back to a more stable version.  Don't recall the video. Microsoft is aware of the issue and a fix is being done as we type this. (I hope).

Good explanation here ..

https://www.accessforever.org/post/error-3048-and-hanging-access-task-in-version-2408