In my case the QDSM Scan Folder function always works to let my user back in as multi-user but give it an hour or so and everyone who left the file is again being told the file is in single-user even though clearly there are several people already using the file. So every day for weeks they text me I do "Scan Folders" again and they are able to continue working. There has to be a reason it keeps falsely shutting them out