I ran into the following issue with my DARWIN-MINI. Unfortunately I did not notice it until I had stripped the plastic gears of the XL-320.
As you can see in the pictures below the servo wire between servo 16 and 14 got caught between the OLLO bracket and servo 16. Which then lead to the servo gears being stripped! So my advice is to routinely move each servo with the power turned off to the robot. This is so you can check for obstructions in each servos freedom of movement.