Is there any information on what might cause variables inside a script to just reset?
I'm getting bug reports of this happening, and the only code inside SkyTweak for this would involve resetting every variable at once, not just one at a time.
And once this variable starts to reset, it continues resetting on a somewhat consistent basis.

It's a fairly rare bug, and I haven't been able to reproduce it, but does anybody know what possible causes might be?

It sounds like the sort of thing you would get from a corrupted save game. Or maybe some strange mod interaction?