I encountered this problem with dark frames about a year ago, but completely forgot about it... It's great that this bug being fixed!
Ilia told me to register on github and report a bug, but I never did that... First, my laptop died, and I didn't shoot more stars then. But not because of a bug or anything, but because of a fact that stars don't look good in 3x3 mode - they disappear periodically. At that time I was experimenting with other things, another camera.. It was probably very unprofessional, for which I apologize.
Anyway, you guys are great, thank you for all the work you have done! Maybe more people will shoot stars now.