@Justoverclock,
If you have time would you be able to install this and fof best answer, then on a desktop, go to a discussion with a lot of replies, and try clicking either like, or the three dot options menu and click on something in the options menu. As you click, does your screen jump up a few posts?
More explanation is in a best answer issue I posted: FriendsOfFlarum/best-answer55
If I deactivate best answer the problem goes away. Or, if I deactivate hashtags, the problem goes away. It seems with both active, this strange bug appears.