For instance when changing resourcepack, a loadingscreen with "Mojang" pops up. If you press the "esc" button during this loading screen, it shrinks and is placed in the upper left corner of the screen. Then you can also look around in the game, until the resourcepack is fully loaded, inwhich a lag spike appears (expected) and everything turns to normal. The only thing to do here is to maybe disable key input while its loading, or make it cancel the whole resourcepack change action.