Tried it again after clearing the cache, and it fixed the problem. Now no dropped frames at all :thumbsup:I'm not sure what is 100% normal since I don't have the downstream to watch 2160p60 videos on YouTube, although I upload in that format to my channel.
I'm pretty sure I've watched plenty of 1440p60 videos without any dropped frames, but I can't be for certain, and while I'd test again right now, I'm in the middle of uploading a few large videos to YouTube so my connection is limited. I imagine a dropped frame here or there could just be a small glitch that happens from time to time (e.g. while switching the quality of the video), and if there's no noticeable stuttering I probably wouldn't think anything of it.
As for the 8K video, that played very smoothly with no dropped frames either. CPU was in the mid to upper 30s mostly..