Imported and scheduled notebooks getting deleted from the filesystem

Problem

We are facing the problem that from time to time notebooks are disappearing on users. When we investigate we notice that they are actually deleted from the filesystem (git marks them as deleted, we have the git storage enabled).

It was very difficult to isolate the problem and we were not able to fully reproduce it but rather gathered the following information:

• (probably) all disappearing notebooks have been imported using the JSON import from the UI
• (probably) all disappearing notebooks have been scheduled using the built-in scheduler from the UI
• there are notebooks which are scheduled but never disappeared; they are probably not imported
• there are notebooks which are imported but never disappeared; they are not scheduled
• there are notebooks which are imported and scheduled but don't disappear
• there seems to be a pattern that it starts deleting from the ones that are scheduled first (e.g. "library notebook" which is scheduled first, dissapeared a lot already)
• other Zeppelins which import but never used the scheduler do not have disappearing notebooks

So it totally looks like something triggered through the scheduling which is somehow related to the import function. I don't know about the internals (how notebook IDs are generated etc.) but it seems that when the scheduler kicks in, something causes a hiccup.

Any ideas?