Two days ago, a user made updates to several modern list items using the default edit form. He could see his changes in the list view but they weren't showing in the individual item Version History for him or others. Also, other users with the same permissions could not see his updates in the list view. As an admin, I can't see his updates in the list view or version history. (I could only see the changes looking at his list view over his shoulder.)
Another tidbit, changes he made to list items 10 days ago worked as expected.
Any suggestions on what might be causing this, or a configuration change I should look into?