So I bought 3 used gunners up and 3 sets of Dogtra electronics. One unit has old rubbers and the other 2 I just put all new rubbers on. The unit with old rubber will work with all 3 electronics. The other 2 will only work with one set of electronics. They all will work without bein under a load.Wondering what would cause that. Batteries not having enough power to operate servo under a load?? Servos goin bad?? Any help would be greatly appreciated!!!