I kept on hitting the stalker (pressed Z after battle ended) and now when i move it glitches.
Is this purposeful?
Nope, looks like you ran into a bug! I thought I added protections against invalid inputs like that, but it's possible I missed some of the battles. Restarting the game and reloading your save should get the game back to normal, though you may need to redo the fight, depending on where exactly it glitched.