1 of 4 Motors firing on battery connection to flight controller

Just built a tiny whoop and when I connect the battery to the flight control board, one of the motors starts zipping away.

I tried different motors on the board and its always the same port, so no a shorted motor. What could be causing this. Was initially fine, then connected to betaflight configurator to test motors. 1 and 2 tested fine. # 3 started but now wont turn off so long as it's powered.