What you need to do mate is try get as much power to the Motor as poss becuase the DM will output a lot less aperage than the FTP. If your using cheap LNB cable or it is old then upgrade it to CT100.
Also as a test disconnect the LNB ans see if it now move correctly, if it does that tell you the motor is not getting enough juice and if you can find a low power consumption LNB then this might also help. If you have a spare knocking around try it.
Ferret