@simmy Hello i too have problem with 3H arcade 2Players controller. up and left not working. One think i can manage is to have 2 players configured. You need to insert at the end quirks line in /boot/cmdline.txt file. :

usbhid.quirks=0x16c0:0x05e0:0x040

This entry enable 2 players in retropie.
But unfortunatelly left and up is not working at all.
In recalbox and windows everything works ok
I have found some info in this thread :
https://retropie.org.uk/forum/topic/4361/20-pin-xin-mo-wiring-diagram-set-up/7
Maybe this is a solution.
I cannot test it right now. Can someone test if changing pins can help ? Is P1 & P2 sides of the board Pin 2 and 4 are dead. ?
Any help ?