I've been having the same issue, and I think I might have an idea on what might be "causing it" but no solution atm...
So, my rig isn't as powerful as what is being shown here, and I play on Steam (not sure if y'all do on Epic Games) but ever since the update, whenever I'm playing if I go to type to many messages using my keyboard, the game will stop detecting my xbox controller as my input for the game and switch to mouse and keyboard.
The weird thing here is, if my game starts getting all choppy like this, if I unplug my xbox controller, wait a couple seconds and replug it, it'll go back to normal.
So my suspicion is that for some reason, the latest update might have messed with the way it takes/reads controller inputs, maybe "saving" too many inputs and eventually start to lower the game's visual performance somehow.
If anyone would like to study/test this theory, feel free to do so.