Update on my problems :)

Received my new $10 BOB last week and tried it today. I plugged only one motor. Works like a charm. Plug all motors, boom same problem as before. Unplug all motors and plug just one. Doesn't work with one motor anymore. I turned off the PC, unplugged everything from the BOB. Turn on the PSU and the motors, thought not moving, make a weird high pitch noise, that they make when they don't work correctly. On today's first attempt, the motor plugged was quite when still. So, I am assuming it's either the motors or the drivers.