alright, had a few minutes to go back to this, and - first sex battle happens after finding the ear clips, as expected - I unequip the clips - next battle, I'm wearing the clips again in my battle sprite - and one of the enemies 'says something strange' and boom, sex time again. I win the battle, and check my character - and head slot is definitely <empty>
so yeah, easily reproduced on my end, which is odd. :\