Dacor RV 30 vent goes up down and back up

When I push the up/down button on the keypad the vent goes up to the top the all the way down and back to the top and turns the fan on high. When I push the up/down button again the fan turns off and the vent goes all the way down and then back to the top and turns the fan on high. I can get the vent to stay down by pushing the up/down button when the vent is in the down position. All button function as expected. Any ideas appreciated.