I have a Genie gcg350ml. One day it would not open. I unplugged the head unit and then plugged it back in. The dorr would open. Then after closing it would do nothing. I was using the wall switch. Replaced the down sensor and the control board. Nothing until I unplug the head unit and plug it in again.. Then the carriage woiuld move to the down position far past the down limit switch but would not move to the open position. Any ideas? Thx.