The shift fork inside the 915 transmission has a very common issue of the tiny M6 nuts/studs loosening. There is no way to tell this is happening without draining the gearbox fluid and dropping the fork plate on the bottom of the transmission. About 90% of the plates we drop show some amount of fretting, and many have damage to the fork from contacting the rotating gears.
We have two solutions in-work.
1: In our shop we have been modifying the plates by milling down the outside of the plate and drilling through the stud holes. We tap the threads all the way through and install long bolts from the inside backing them up with locknuts on the outside of the plate. This adds many additional (fresh) threads in the magnesium/aluminum plate, and locks everything in place with the nuts. This is a great solution, but will require an exchange of the plate to provide this service to our online customers.
2: We are also working on providing a new plate with the through-bolt solution. This just requires some time to develop, after we finish a few more pressing projects.