lr-mame2003 Retropad mapping interferes with keyboard mapping

[caver01]

I am trying to map controls in lr-mame2003 using the retroarch.cfg to setup my keyboard bindings (I use an iPAC-4 and no gamepad controllers). The problem is that within mame2003, keys seem to bind to both my keyboard and a "retropad#" controller AT THE SAME TIME. This is very frustrating. I don't want to map to a gamepad.

For example, I am trying to setup mapping for player 3 in Gauntlet. If I configure my retroarch.cfg appropriately with UP corresponding to my P3 joystick pushed up (which is sending a keyboard key via iPAC), it also seems to be auto-mapping to a "Retropad3" controller in addition to my keyboard setting. In the case of this game, I have the cardinal directions rotated 90 degrees because I have a 4-player cocktail cabinet design, yet because it's also mapping a second controller automatically, I can't stop it from having a combined set of inputs. If I look at the mapping inside the MAME GUI and try to remap a key, it picks up this phantom retropad controller in addition to my keyboard keys. In this game, it is combining two inputs so my player moves diagonally.

Is there a way to simply block these retropad 1,2,3,4 controllers from showing up in mame2003?

This is RetroPie 3.6, built from image, MAME 2003 recently updated from binary.

Thanks!