ESC trouble?

[HockmanRCBoys]

OK.....I recently purchased a used Holmes Hobbies BR-XL esc for my SCX-10. It came with a BEC wired to it, which I've never done before. I've always wired BEC straight from battery to servo and used the RX for signal only, so this is new to me. The esc is doing something I've never seen before. After releasing the throttle, the motor hums/pulses a bit. Also, when the drag brake is engaged, it does the same thing. When the truck is sitting still, you can barely move the spur, and it does the same thing. Tried more than one motor, same result. I just find it uncanny that I've never seen this problem before, and this is the first esc I've had with a BEC wired to it, and powering the RX with. Yes, I did remove the red wire from the esc plug.

Help please! Thanks!