Thank you. We are in a school environment and turning off autosave is risky indeed. The only time they seem to loss file is working off the desktop or my documents, which are redirected to their personal network drives. No issues EVER working form the local hard drive.... I has to be a windows netowrking thing
I have seen this problem for years in various versions of AutoCAD and Windows. I believe it is related to the way AutoCAD (mis)handles its file-saving process.
I think the random file-locking feature has something to do with (particularly on wireless) network re-authentications either failing for a short while or affecting session tracking. I now edit locally and use Free File Sync using two-way sync and with deletion handling set to "versioning" to sync the network drive with my local copy (which is also in DropBox). The only shortfall is that it doesn't lock the network file when I edit it. I can set it to read-only if I want but that's just a convention that can be fragile
One way I have worked around it is to "save-as" to the UNC path over the top of the file the mapped drive thinks is locked.
Also, look for "blahblah.ATMP" files - they are your drawings. change the extension to .dwg and open them. Look for them by date/time to find the latest vanishing act.
I had an on-going bug report about this with Autodesk for years (literally) before I just gave up on it (and their support). They only fix things their sales department tell them to fix. Shiny things.