Reported: Ammo in the ammo slots cannot be unequipped. Clicking it or dragging it back to the inventory does nothing, and it only leaves the slot when replaced by another ammo type or used up.
Found: The server's unequip only looks for the item among worn equipment (weapon, armour, shield and so on). Ammo sits in the separate accessory slots, so the server finds nothing to remove, refuses the request, and the ammo stays where it is. Replacing ammo goes through a different request that does handle those slots, which is why swapping works.
Planned fix: Unequip will accept items from the accessory slots and move them back to the inventory, provided there is a free inventory slot. Work on it is starting.
Also affected: Rings and amulets use the same accessory slots, so the same fault should stop them from being unequipped too.
To verify: Once the fix is out, equip ammo, then drag it back to the inventory. It should leave the slot and appear in the bag. Repeat with a ring and an amulet.