Refunding In-Game Items

Ever since since Season 5 officially came out (excluding pre-season), the refund in the shop (Summoner's Rift) is functioning in a way that it will sap a percentage of your HP amount for whatever reason. For example, if I buy an extra pot and I refunded it, it'll drain a chunk of my HP. Whether this was intentional or not, I would like to know why this problem occur frequently and almost certainly. WHY?!!?!?