Encountered a bizarre issue with videos on Twitter with Pale Moon on Linux, precisely on this month's build of Manjaro Linux KDE Edition. Sound is messed up in a way as if its pitch was lowered. If I replace the user agent override with an empty string so it uses the default string, it works after refreshing the page.
Example video so you don't have to look for one; see if you can hear the guy talk normally.
Pale Moon was installed from the distro's repo, no addons installed, just default settings were used. Can't reproduce on Windows (x86 or x86_64 version). I've yet to try a less bleeding edge Linux distro. Can anyone confirm an issue on their end?