Every time i refund an item in-game i lose hp and mana.
one time i did this and a jinx ulty killed me, i was full hp in fauntain and refunded an item.
1. be in game.
2. buy an item.
3. refund that item and watch your hp-bar.
this could be because i bought the item when i was lower in hp, than refunded the item and than my stats went back to that moment i bought the item and my hp bugged.