I've already sent in a ticket to support, and to the numerous affected channels, but figured I'd speak of my troubles here for those wondering "anyone else have this problem?".
So since updating to v7 build 9021, I've had daily problems.
1) Some channels get stuck in a buffer loop that won't go away, which is quickly fixed by resuming again. Channels that do this often for example are FXNow, Funimation, and Crunchyroll. Even troubleshooting with extremes on my own network (student in networking/power user here), can't solve it. But I assume this is more of a developer updated needed situation due to the OS update.
2) When the above repeats multiple times (I usually do a quick resume every episode or every few depending on the channel), after so many times the video stops playing, audio continues, and the Roku 3 keeps playing catch up with video frames speeding along. During this time the unit isn't responsive at all via the remote. Sometimes after 15 seconds or so of this the unit will allow me some control, or will eventually just freeze and reboot. In either case I need to reboot the unit.
To me this sounds like a temperature problem, but the issue is as amazing as it sounds my unit is rather cool, no hotter than a DTA box I have, cooler than the air spitting out of my water cooling loop for my PC CPU and...you get the point; it's in a well-ventilated area, so I'm positive it's not overheating.
All these problems started happening exactly when the OS/firmware update rolled out--couldn't be happier with the product before it, for many many months. Some users report similar things here: viewtopic.php?f=28&t=90974
Roku 3 (4200X)
v7 - 9021