Like most of you, I have been having the same problem. Woth youtube as my primary way to watch TV, it is a tad frustrating. I had tried my account on every device to no avail. The roku tv just pauses and buffers, my firestick will continue to play the video but will stay at a still image on the screen, and my Xbox does the same thing. It's only on my main account though, I have a secondary account and everything seems to work fine on there. It is a business account though so i don't want to use it daily and muddy up the recommendations on that account. I know it's not my internet because the second account works fine and I have excellent connection strength. I have tried everything, I might just resort to watching youtube on my iPad because I don't know what else it could be.
