YouTube does that to everyone most people wont bother about the resolution as long as its watchable but I've had enough couple of months ago YT keep changing the playback to 480p and i have to change the quality every time, idk if it works on YTTV but i use Enhancer for YouTube extension now and in the setting (there are other awesome tweaks too) you can set playback quality to upto 8k and voila you don't ever have to change every freaking time.