@demonscythe Hey!, I never got this resolved unfortunately. I stopped using the Piboy and got an Odroid Go Super instead, because of some multiple reasons. Maybe if you post your log here others may be able to help out. I don't know if ExperimentalPi's script auto makes the DMG controls 1st player, but that is also something to ask them about. Let me know if I can help in any way though.
Please do not post a support request without first reading and following the advice in https://retropie.org.uk/forum/topic/3/read-this-first