Hacked DC controller only works if I unplug and replug it after startup, help!

I just hacked a MadCatz Dreamcast pad, and when I turn on the DC the start button works, but once I get to a menu the buttons all stop working, as does the up direction. If I unplug the controller and then plug it back in all the buttons and directions work. Also, sometimes I have to unplug and reinsert the VMUs to get the Dreamcast to recognize them. Does anyone have any idea what could be causing this?

I’ve been trying everything I can think of and still haven’t found the problem. Is it possible that the Dreampad isn’t common ground?

I would guess something funny is going on with the up button wiring/soldering, but I don’t know why replugging would make it work fine.

If you take a picture of the pcb, I could probably tell you if it’s common ground or not.