I'm in Ubuntu at the moment and decided to fire up Firefox to use Tubalr for a change. I found that when dragging a video (say, to rearrange them), the currently playing video changes to the video that you just dragged when you release the mouse button.
This happens when dragging new videos into the playlist as well.
This has been reported by a few people, thanks for logging it here. It's a pretty annoying bug.
I wouldn't say this issue is non-critical, as it makes users want to avoid using DnD so they don't trigger the bug.