there are two ways.
Run OpenServer (green flag), click on it, find Phpmyadmin, open it, login to phpmyadmin (login root, pass - empty (no password at all)), select your database at left bar, then click on "SQL" tab on top, and enter next there
update `char` SET head_top=0, head_mid=0, head_bottom=0 WHERE `name`='YourPlayerName';
Replace "YourPlayerName" in the line above.
It will set no headgear for your players when you will log in, but they will be equipped. Then when you just logged in, do command @storeall, or @dropall
Second way:
Repair the item sprite with Server Database Editor. Find your item what you have equipped, and press CTRL + G. Save, and log in to the game to test.