I only have Xkey (25 keys) in hand, so I tested it with Xkey Plus, I can make the program change to #32, please check attached screen shot. When you assign the Pitch Up button to PC, it will switch to “single” mode automatically, so it won’t be controlled by “velocity” data, I do not know why you had this problem. Or maybe Xkey37 has some issue with its firmware? Please try to do “Reset to factory” in Xkey Plus first.
(If you cannot see the screen shot, please check on Facebook though below link)