Hi - first, I tried the executable you provided in private, as well as the newest 1511 build, and they still behave the same.
I can also practically now confirm that the issue happens every time the PC resumes from standby/sleep (after a few hours of standby) -- you should look into that, possibly a time sync issue as I explained above.
Second, I enabled logs a week ago, the app requested to re-validate the license several times since then, but there are no logs.
I will likely move away from Enpass given this issue, but more importantly the mobile issue with calling home and SSL (reported here) -- I can't accept being locked out of my password vault because the app wantrs to call home. I'm willing to spend a little more extra time to help resolve this one.
In the meantime, where can I download older versions of Enpass? I need to be able to rely on being able to open my vaults.