mystic shoal
I'm also a game dev as well,
I think it's happen because you don't limit the number of cards on hand and it call too many Lean tween animation,
To fix this maybe you need to limit the number of cards on hand eg. 50? I don't know,
Or just ignore Lean tween animation when have more than 20? cards on hand.
To reproduce just make a condition just like my 2nd picture.
pliant stratus