possible causes
bad reading- play maps that are harder to read, it will help with aiming the circles instead of just randomly moving your cursor towards them
inconsistency- just play maps inside of your comfort zone, it would be best if the maps were minimum 3 min
uncomfortable grip- you can choose a grip that restricts your hand movement more, it will be easier not to overaim once you get comfortable with it
bad finger placement on pen- if your aim is off try experimenting with your grip finger placement while not changing the grip completely
bad aim- play more, too much force when dragging?
uncomfortable surface- try covering your tablet with a mousepad and see if that helps, it also helps to restrict your hand movement a bit by having more friction which can make it easier not to overaim
edit: ur a mouse player? then try adjusting mouse grip and play more
personally when i sometimes play with a mouse i use a finger only grip
i struggled with overaiming aswell but i found out im just inconsistend any my hands like to do a lil rng flick here and there