Hello!
Having the same problem. The issue started after the last patch (1.2.4.). The problem starts when I'm giving Ashara the PvP Centurion Weaponmaster's headgear. When I remove it from the slot, the head comes back. I haven't checked if this also applies for other types of headgear or other companions.
Hope this will help to create a fix.
I have the same problem with the Recruit Weaponmaster headgear.
Best regards,
BenAndros