Seems the controller can’t “look ahead”. No prints on the job? If not, your gonna have a tough time. If so, start scouring the down direction circuit. D, DX, SD or whatever is in the down circuit.
Like Turbo asked; “what controller?”. If it’s a Miprom 21, check the encoder coupling. Loose set screws, broken spring type couplers will seem fine in one direction but give grief in the opposite. Faults will be generated on an encoder problem. Or, as was mentioned the encoder itself, but rule out other possibilities first.