https://bugs.freedesktop.org/show_bug.cgi?id=104597
--- Comment #15 from Michel Dänzer michel@daenzer.net --- (In reply to Luke A. Guest from comment #14)
It's been pointed out it's not Obs as TyMiles2012 moved back from the Oibaf PPA on Ubuntu 17.10.1 back to standard drivers and it no longer affects him.
That doesn't mean it's a Mesa bug, just that the OBS issue was triggered by a change in Mesa's behaviour (it now exposes 10-bit-per-component colour configs).