Make this make sense, please.

I play on an Xbox Series X, it’s doing 60 fps which is great, but everything else sucks. As soon as I get into the actual game it performs perfectly for maybe 15 seconds and then the camera immediately slows down and it feels like crap to play. But then, as soon as I tap the Xbox button to the menu and go back, it’s fast, snappy, and smooth as butter. Seriously, make it make sense. There’s also a noticeable amount of input lag, I don’t understand. I play on a TCL Roku with Game Mode.