Joystick (or trackball) Remapping Paralyzes Joystick

I’m using the game Star Wars under Mame-LR, 2003 version, on RetroPie. I want to reverse the direction of the Y axis on the joystick, which feels more natural to me.

From within the game, I pulled up the Quick Menu and swapped the UP and DOWN inputs on the DPAD (which my joystick is treated as). I double checked to be sure I had reversed these two items and the associated keys, but when I resumed the game, the left/right controls worked, but the target site would not move up or down at all.

What am I doing wrong or what do I need to do? How switching the up and down bindings lead to no motion at all?

Also, I found out, almost by accident, that my trackball would also control the target site. Is there a way to reverse the Y axis from the trackball input?