This solution was posted in the German forum, hope you can see the pictures
http://www.xt-660.de/forum/viewtopic.php?f=19&t=16699

He removed the locking system and disassembled it. Then he polished the small metal plates, which are responsible for the locking (pic no.6). He used a micro motor grinder and a rubber-bonded polishing point.

This seems to be a long term solution.

Ciao
Solitario