I've just had a quick look at that adjuster and it's screwed in very tight, I haven't moved it but if it was there to stop the crown wheel moving when under load I would expect it to be just in far enough to touch the back of the gear, it appears it may be over tightened.
In the service manual it only shows the screw and locknut which runs in a grove on the back of the crown gear, there doesn't appear to be anything attached to that screw on the inside of the cover, or no part listed in the parts list anyway.
The manual doesn't give any info on the screw other than the torque of the lock nut
I'm thinking about undoing it and screwing it back in until it just touch's the crown wheel, any thoughts ?