[martin417]

In 2008, we had similar issues. If I had it to do aver again, I would use a brake to hold the load, and turn off the motor. DC motors do not like to be stalled, they heat up very fast. If you are using pneumatics, try a small cylinder pushing against something in the gearbox. Maybe a UHMW pad against the pinion gear? Every time you set motor to 0, turn on the valve to extend the cylinder.

An excellent solution would be a bicycle disk brake on the arm, actuated by a pneumatic cylinder.

In 2008, the problem came up at competition, and with no time to implement a mechanical solution, the programmers just put in a routine to pulse the motor when were at the extreme. Not an ideal solution (we still had issues) but it helped.