I recently bought three GBM8108 motors. Two of them work flawlessly, the third one has an odd problem: Whenever I connect it to my Alexmos controller board, the motor becomes very hard to turn, i.e. there is a lot of resistance. Both when the board is powered on and when its without power. Performance-wise, this makes the motor very slow to respond. I'm trying to use it on the pitch axis, where it stutters and struggles to follow my moves. Every movement is delayed and slower than it should be, as the motor fights against some internal resistance. As soon as I disconnect the cable from the board (leaving the other end plugged into the motor itself), the resistance goes back to normal, and I can easily turn it. I've tried hooking the motor up to all the other connectors on the board (X, Y, Z axis) and nothing changes. It also makes no difference whether the board is powered or not. I then used different cables from my other motors. Same result. Any idea what's going on here? I guess the magnetic resistance of the motor increases when something is connected to the servo cable, but I don't know enough about the technology to really make more than an uneducated guess.