Does this happen when using the keyboard UI?
A possible workaround would be to enable the 'hide helmet' option on the equipment screen (when using the keyboard/mouse) and save the game; helmets would continue to be hidden loading the save with the controller UI.
Try verifying local files: in the Steam library, right click on Divinity Original Sin Enhanced Edition and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
With the GOG version, in the (optional) Galaxy client, select Divinity: Original Sin Enhanced Edition in the left column, then click on the More button, and in the Manage menu select 'Verify / Repair'.