So, for some reason I've had this issue that I never used to have. I've always been able to run this game just fine, but a few updates back, I noticed that if I was in a single player world, the game would lag horrendously for seemingly no reason whenever I was in full screen. The framerates would drop, but also the controls would almost always be unresponsive and if I'm in a Discord call, nobody can hear me when this is all happening. I reported this bug before, when this was the only issue. Since then however, it's gotten worse. Not only can I not just play in full screen now, I just cant play single player at all. Even when the game is windowed now, the same stuff happens. I've uninstalled and reinstalled the game on numerous occasions, and it never fixes it. I'll try it again, but I doubt it'll make a difference if the past is anything to go on. I can play multiplayer games just fine, like servers and games with friends. Those work in full screen, too. But single player... I guess that's just asking too much.

Here's the old report: MCPE-98715

I read the comment I got, but the confusing part is why it never happened before. Even so, I disabled Game Bar as suggested, and it made no difference. I just can't pinpoint the issue.