When you said there was a one volt drop across the main contacter, stop right there. The normal voltage drop across any contacter is.1 to.3 volts. One volt is too much. Second, make sure you dont have a weak battery. Load test then all, one at a time. If you dont have a battery load tester, run the lift with voltmeter. Use min/max to test battery on start up. If there is a weak battery, voltage will drop to 17 volts. You cab only see this with min/max.
Unplug battery and check for shorts to frame. Dirty comm in drive motor or lift motor will cause issues