to put a UIT on the controller you will have to to the factory and get new software. You can put a UIT on the door operator if it is one of the newer PA boards (6300HL1 is the UIT part number). But an HD98 should be the older PY or even older FX boards. These older boards will act like this when they get old where you can’t get it to slowdown. I’m not really sure where you can go from here without IMS though, can’t do a scan or make adjustments. Do make sure it has the correct encoder though and use a meter to verify it works. The older boards get the big black optical encoder, the newer PA boards get the small digital encoder.