Deck 2 pitch slider with Denon MC6000MK2 only goes up on both iPad lates version and McBook Pro.

Using a Denon MC6000MK2. Deck 1 pitch slider works ok with controller but deck 2 pitch slider only goes up. When I push it down, it remains in the middle. I tried all possible ranges (8%, 10%, 25%, 50%, 75%). I can push it down manually on the iPad and with the mouse on the MacBook Pro, but once I do that if I try to move it in the controller it gets stuck until I load a new song into the deck. Please advise.