After picked up Illuminated Mushroom changes to normal default head and causes a crash every time inventory is open. The item still counts for the quest which can remove it, but it still drops from mobs so after the quest step the only way to remove it is to throw it away after few crashes. Update: The slot that was used to throw the item away is how gliched and causes a crash when inventory is open or when slot is used. Update2: Luxic Plasma was gliched on 1.9 and made the slot where Illuminated Mushroom was the crash trigger. After changing to 1.12.2 the plasma registered correctly and the bug stopped.