I have seen low power from an open phase in the motor. Also could be a defective controller. Check the voltage across the three phases once you get it running again. Have you checked the controller settings to se if they are set correctly?

we have installed two controllers due to believing it was a controller problem as by the controller rebuilders. original problem was little to no travel and no codes, constant testing caused controller to overheat- gave code 41. called hyster ,they came in and hookup laptop,cleared the 41 code and saw that motor was pulling 650 to 700 amps, I pulled the motor sent it out to a rebuilder. Was told that motor was shorted due to junk built up inside motor. rebuilder sent it back stating it tested fine once it was cleaned out. I reinstalled the motor,test ran - no change-little to no travel. another tech said the encoder was an issue so I disaasseembled the motor and replaced the encoder,reassembled and test drove,got the 52 code this morning, i hooked up the original encoder and no more 52 so I just pulled it apart and found wiring to encoder had moved and had been cut in two by motor head. I've just repaired wiring to encoder but haven't install it yet. I did troubleshoot the 52 code by using the old encoder and the lift went back to little to no travel, no codes so I believe that the encoder is not our problem but I'm at a loss at what it could be.

Was the original problem low power and overheating with no codes?

Code 52 is a speed sensor error in the drive or hydraulic motor.

i think ive figured it out, the new encoder bearing is no good. I hooked the old one back up without installing back into the motor, code 52 went away, I am now back to my original problem of little to no travel and no codes till traction controller over heats because high amp draw from traction motor. we took the motor out sent to a motor rebuilder. they at first said motor was shorted but then said it tested fine once it was cleaned out. reinstalled motor, hookup battery test drove no change it was at this time that i was told to change encoder bearing in drive motor which gives me the #52 fault code. i am at my wits end please help!