Since the upgrade to Roku 2.3 on a Roku 4200, it seems that I have noticed as I FF through commercials a few blank frames. And I also seem to have noticed that if I switch from 1x to 2x or 3x FF, the switch is kind of jerky. It stays on 1x and all of a sudden zooms a few frames to 2x.
I'm still on Roku OS 7.7. When I see the blank frame again, I'll try to unzombie my brain to backscan and see there is a blank screen in that area.