We are experiencing the same issue with QS version 3.1 SR2; we just installed QS version 3.1 SR3 but based on this thread, the problem will persist
We had two QVF files corrupted over the last 7 days, in both cases the QVF was located on a network drive (the same server in both cases, two different developers, both working with QS version 3.1 SR2). A third developer currently on leave has not reported any issue, but we believe all his Qlik Sense applications are located in his workstation, and he is working with QS version 3.1 SR2.
Are you experiencing this issue while saving the Qlik Sense Application to a network folder or locally in your workstation?
Getting the exact same issue with SR2. What I've done is created backups for my qvf. files so whenever 1 gets corrupt I replace it with the backup. I know its not a solution but can work till the solution is worked out.