Similarly, we have used the package for over 10 years (on a network) but never had a problem until this past year, and the file always corrupted after someone had worked in it for a period of time.  ProSeries tech support advised us to exclude the client file directory from the virus scanning software, which we did, but that did not resolve the problem.  At the same time, we were experiencing a problem with Windows Explorer (via Windows 10) shutting down randomly multiple times a day (often when you had more than one window open).  We determined that our group policy and drive maps were disconnecting multiple times a day and reconnecting instantaneously (similar to a IP lease reset on a network).  In short, the person working in the FAM file never knew it was occurring while working in the program.  A slight tweak to the group policy and drive maps by our IT guy fixed the problem.  Moral of the story:  I suspect the program is disconnecting from the underlying FAM client file while your working in it.  But, as I said, you'll never know it.  You might be able to isolate a root cause of same if you're on a network or place the client files on a 'remote' drive.  Hope that helps.  We have not had a problem with the FAM package since.  [And yes, the thought of recreating a file is nothing short of a horror show.]