This was happening in November nightlies for me and it's still and issue in the stable release.
It's not a huge deal but it can be really annoying.
You know the open recent/open apps button in the bottom navigation bar?
All the other ones work but this button stops functioning relatively frequently, but of a pain because that's my main use for that tablet ui navbar.
By not functioning I just mean it does nothing when you press it, it's just a inactive button so to speak.
I can fix it (temporarily because it stops working again and again) by going into settings > interface > [navigation bar] buttons and layout.
And then just reset it.
Love the rom but this happens too frequently its quite annoying, anyone else have this issue, it's kind of a silly issue I hope there's some fix.