Currently the game tells me my Cash Shop Inventory is full after I took out some nx equips. However, I can't take out anymore from the Cash Shop nor can I put any back in. This applies to all cash shop items currently as I tried to take out gachapon tickets and it wouldn't allow me to do so. EDIT: Ended up fixing it by taking out stuff from the cash shop first before trying to add any in. However, I think this will still be a problem eventually when I acquire too many hats from jump quests haha IGN: ItzyRyujin
We give sufficient Cash Shop space. If you really need to hoard that much NX, do what @Alvina suggested and make mules for extra storage.