Lately, me and my guild mates encounter this issue and its rather quite scary I would say.
What happened is, I simply just un-equipped my costume, instead of it went to my inventory, It drops to the ground immediately. The "Lock Item Drop" on the inventory was also up. Lucky for me and my guildies that it happened when we were just chilling on our GS.
Can someone on Warpportal check into it please? It creates huge paranoia, and we felt uncomfortable to un-equiped anything while opening kafra in the busy town.
My item was Mid-headgear costume elven ears, and one of my guild mate drops her costume devoted eyes. (Gonna check for the rest of my guildies of what item that dropped). So probably there is something is not right on the Mid-headgear costume section on equip window. Please look into it. Thanks!