I removed a Nisfit"s riveted plate helmet from a High Elf today and it vanished.
This problem still exists.
I hate that it takes so long to get a Nisfit's rivited plate and a Ingrimm's hood replaced because I have 2 Units with each helment I need to Dismiss and upgrade to a Archangel or High Elf and I know the hats will vanish when I take them off.