All of my PC's have been experiencing an issue where their max HP reverts back to their level 1 state. It seems to happen to random PC's each game and is at least 1 every session often more. We are rolling for HP but are about to revert to averages as we no longer know who is supposed to be at what. Would love to know what's causing this and maybe a fix? PS running D&D 5e using the default character sheets.