Extremely strange Bluetooth controller button mapping problem

[Fightan Magic]

Hi all,

I'm having a bizarre Bluetooth controller problem. It's a little hard to explain but basically, once I actually fire up an emulator, the button mappings go totally haywire. For example, the Start button gets assigned to the left trigger (button 8) while the A and B buttons cease to exist, and other weirdness like that. I've been having a hard time tracking down what precisely maps to what. It's consistent, but illogical. It happens in all games and emulators.

So, a few details. Pi 3, onboard Bluetooth. Using Retro Pie 4.2, latest stable image from this site. Gamesir G3s controller. The controller itself seems fine as far as it goes. In X-Input mode, everything is fine in both game and menus. In Bluetooth mode, I can navigate Retro Pie menus fine with the buttons as they should be, but it goes berserk once in an actual game.

I checked the auto-generated configuration in /opt/retropie/configs/all/retroarch-joypads against the jstest program. Everything tests out as expected. I tried doing a system specific override with this file, but no change. I also tried the 8bitdo button mapping hack, even though it's not an 8bitdo controller, but it seemed vaguely related. No dice. There is no firmware update available for this controller as far as I've been able to find, although firmware updates for Gamesir controllers appear to be wonky at the best of times.

I've pretty well exhausted my knowledge at this point. Any ideas?