[TubaMorg]

We had the same problem. You would hope that the worm gear would keep it from backdriving, but it doesn't. So we went with the Keyang instead. Programming won't help "lock" it. You are talking about running the motor at a stall (just enough voltage to stop the movement), which is never a good idea. Think about a design mod to solve your problem. Teams in the past with this sort of problem have added in a locking mechanism (like a brake). Or you can try the Keyang motors, they don't backdrive.

Good luck!