Firstly, I think you should go buy a tube or can of Di-electric grease and take all the control switches apart and clean them and lube them with the grease. This will ensure that your motor's get the voltage they need.

Then freely lubricate all your connections with it. It's thick and good!

Maybe remove each motor again then bench test them BOTH directions, re-install them, if they struggle to lift or dont lift at all they likely need rebuilt...

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