@quicksilver
It had passed 4 months before I actually tried your fix proposal.
It worked. The X-box controller is now fully compatible. Thank you!
@rodolfoaguilar @Firebird_WS6
I'm summing up what quicksilver proposed.
This solution worked for me.
Plug in a Keyboard
While in Emulation Station press
F4 to open the Terminal
Type
sudo nano /etc/modprobe.d/xpad.conf
Change
xpad triggers_to_buttons=1 to
xpad triggers_to_buttons=0
Press
cntrl-x
Accept the changes.
Return back to Emulation Station by typing
emulationstation
Restart Retropie.
(In my case, I noticed that the X-box controller had started acting strangely while in Emulation Station.
The D-pad buttons swapped positions in Emulation Station as they were previously in PPSSPP.)
Remap the controller in Emulation Station.
Remap the controller in PPSSPP if necessary.
(In my case, this was not needed.)
I'm not sure why this issue is affecting some people and not others.
Apparently, the problem is caused by the Trigger buttons somehow.