We had a lot of intermittent problems with an O & W car because of a 50 to 70 volt control voltage drop when the doors opened. It turned out to be a bad selenium rectifier feeding the main control voltage. The rectifier must have been breaking down internally causing a large voltage drop under load.
You can just replace the selenium rectifier with a postage stamp rectifier as shown in the controller image. You should read about 200 to 210 VDC if the rectifier is good.