In current firmware when plugged into 'IN1' port on a Latitude receiver the Thumbwheel will override control of focus. You will need to make sure you have focus control disabled on the hand Controller because otherwise this can cause the motor to lock up or jitter back and forth.
You do this via the Controller MENU - INPUTS - AXIS - FOCUS - OFF
Second thing to try is make sure you have the AUX port configured correctly. It should automatically detect a Thumbwheel but if not you can manually configure via the Controller MENU - AUX - MODE - KNOB
If neither of these is solving your issue please open up a support ticket by sending an email to 'email@example.com'