Its frustrating too, but just found out how an out of scale note can be used. I still wonder if I should have ever started with this piece. On the other hand it forces me to really understand things. Last two days working on something new. Getting fed up with moving the same notes around over and ov...
You could try.
Uninstall lmms, after you backed upped anything you don't wanna loose.
Then delete all lmms folders if any are left.
Run cccleaner.
Reinstall lmms.
https://www.piriform.com/ccleaner