Kishorelal Deva came across this procedure some time ago.
- Start the car with the foot on the brake.
- Put it in first and then back into neutral wait 5 sec.
- Repeat the procedure 10 times and then switch off the car.
- The gear "creep" should now be adjusted.
This might explain how an adjustment is made as the clutch plate wears in normal use (though the auto-adjuster in the clutch actuator should also do this).
It has worked for more than one when unable to select reverse when other changes were OK.