Videos on every content site that I've tested so far (especially notable for YouTube though) are having many issues buffering and suffering general slowness after reinstalling Firefox recently. To describe the issue more specifically: when opening a YouTube video, the video is very slow to load and sometimes causes Firefox to become non-responsive. When the video loads and starts playing, if I pause or skip to a certain point of the video (forwards or backwards to points that show to be currently loaded), the video buffers similarly to when starting the video.

I have tried disabling hardware acceleration, clearing cache, and clearing cookies, but nothing as worked. Is there another possible solution to this problem?