1 of 1 people found this helpful
Since you are using FMP as the host and not FileMaker Server, the "save a copy as" is your only backup mechanism. Almost impossible to say what the cause is without an in-depth look at your deployment.
I would strongly recommend going with FileMaker Server. That way you can safely take as many live backups as you want.
Problems like this have been posted here for Server, but might effect Client too
( unfortunately, it seems you can not browse archived threads. This is really dumb )
The basic idea is that FileMaker just stops writing to disk, for an extended period of time
Since it is not easily repeatable, it is difficult to fix
it might pay to call Tech Support