G.I. Joe 4 player mode cannot set controller input for players 3 and 4

Not sure if this is the correct place to post/ask.

  • RetroArch v1.9.4
  • FinalBurn Neo core v1.0.0.03 ac6204a

Using gijoe.zip, 4 player mode requires setting a dip switch:

Once the dip switch is set, I can see the 4 player screen:

Port 1 is auto-mapped, no problem:

Port 2 is auto-mapped, no problem:

Port 3 is not auto-mapped, and cannot set any keys:

Port 4 is not auto-mapped, and cannot set any keys:

Can anyone help?