That’s a different bug. This bug was about videos not playing at all. Please open a new bug report about intermittent playing. It seems some are also experiencing dropped frames, which may or may not be because of the same underlying bug that you are experiencing. It would be great if someone could write a bug report about that one as well. I’m closing this bug now so that we can get the discussion moved to threads specific to the new bugs.
[edit] A new bug report was created: No HW acceleration in video playback