When playing audio or video in a tab, opening a new tab / switching to it causes the audio/video to stutter
When I am playing media in a tab (youtube, spotify, etc.), if I open a new tab + website to browse, the audio/video in the other tab stutters badly.
This happens no matter what. With add-ons enabled, with ALL add-ons disabled, AND with firefox in safe-mode.
I have uploaded a video of the problem in action: