I’ve had three support calls in the past month. Folders in the mailfile reorganize by themselves. I observed it happen on one PC. The user dragged and dropped a folder into a sub-folder. When they released the mouse, others folders began moving around automatically. It was somewhat like watching a virus at work.
We made new replica’s of the file to the server and replaced the mouse and drivers. It hasn’t happened again since I then. I wish I knew the cause though.