That is frustrating. The motor should be able to draw up to 7 amps if its the original DC motor. The original lenze 534 controller was set at 8 amps max. Are you using the Lenze driver module.... if not whatever you replaced it with may have a problem with the ramping circuit something like a feedback resistor or amp has reduced gain due to damage from earlier brush problem. It responds but slow in outputting extra amps under load.