Amx 4 error 469

hello i have an AMX 4, this machine need a calibration, but when i tried to do the GENERATOR CAL this error appear, exactly when i try to do KVP cal, mAs is ok, in the process of KVP CAL 52 kvp is ok, 64 kvp is ok, 85 is ok, but when i try 120 kvp cal this "error 469" appear.. please i need to know troubleshooting of this machine.