how to permanently anchor accessories to a npc's head?

whenever i make npcs in roblox studio and close the file, then come back to it some time later, the accessory(hair, hat, face, etc) is glitched inside the head, not on the head. in order to fix this, i have to delete the accessory and replace it with a new one. i don't know how to be the most specific, i'm just wondering how to stop the accessories from glitching. (i use a plugin called easyinsert)