I am finding that preferences for Scrivener corrupt after usage. I see that sometimes I cannot hit return and have a return be made. Correcting this involves trashing prefs. And in what may be a similar bug, colors for labels can’t be edited. Is this just me?
I would say it was just you, unfortunately. 
When you say that if you hit a return, one isn’t made, is that in the main editor? (i.e. Not in the corkboard or outliner.) And how are you trying to edit the colours for labels? (You do so by double-clicking on the colour square in the Labels & Status Setup sheet next to the label you want to edit.)
Let me know any details you can think of, as this does seem very strange.
All the best,
Keith
It sounds like you have had this problem more than once. If you could find the precise steps to make it happen again and document them, that would help a lot.