Then the voltage settings in the controller must be set higher than the actual voltage is, and is causing your problem. (they might call it "lack voltage" or similar, don't know for sure what yours calls it; there may be more than one setting for this).
If all the settings are correct, then something is wrong with the controller. Before replacing it, you could try writing down all the settings then resetting them to factory defaults, and then manually resetting each setting to what it should be.