This has been an issue since before the winter update, but I held from posting because the update was imminent. Randomly, every so often, I’ll start up the game, and it will be capped at 20fps in menus and during matches, with cutscenes running at 30fps. Normally, I get 60fps (capped) without any drops (my rig is more than capable, even before all the performance fixes). In order to fix this issue, I have to reboot my computer (simply killing and restarting the game causes the issue to persist). Worth noting that my Nvidia drivers are up to date.
This happens to me too. I just put the game to full screen then back to windows mode and it’s back to normal.