GameCube L & R Triggers have 99% dropped inputs

Summary

BizHawk 2.10+ almost never responds to pressing the left or right triggers on my original GameCube controller plugged in over the Mayflash GameCube adapter. I do have the springs removed from the triggers if that matters.

Update: I noticed an in-game indication that the R button may be being held down, but I don't know of a way to view what raw input the program is seeing. In BizHawk 2.9.1 and older the buttons are reported as "J1 B5" and "J1 B6", but in BizHawk 2.10 and newer they are reported as "X4 LeftTrigger" and "X4 RightTrigger". Perhaps BizHawk 2.10+ does not really support mapping the digital trigger buttons separately from the analog trigger ranges?

Although the symptoms differ, which BizHawk versions work follows the pattern observed in issue #4647, so it sounds like an SDL issue. However, in my case rebooting had no effect.

Repro

0. Have an original GameCube controller (maybe without springs?) and Mayflash GameCube adapter.
1. Load Bizhawk 2.10 or newer.
2. Load a game.
3. Attempt to update the controller config. Trigger buttons almost never respond. Same effect in games.

Output

Log Window output when unplugging/replugging the controller.
Broken versions:

Disconnecting SDL gamepad, device index 0, instance ID 7, name Mayflash GameCube Controller
Disconnecting SDL gamepad, device index 1, instance ID 6, name Mayflash GameCube Controller
Disconnecting SDL gamepad, device index 2, instance ID 5, name Mayflash GameCube Controller
Disconnecting SDL gamepad, device index 3, instance ID 4, name Mayflash GameCube Controller
Connected SDL gamepad, device index 0, instance ID 11, name Mayflash GameCube Controller
Connected SDL gamepad, device index 1, instance ID 10, name Mayflash GameCube Controller
Connected SDL gamepad, device index 2, instance ID 9, name Mayflash GameCube Controller
Connected SDL gamepad, device index 3, instance ID 8, name Mayflash GameCube Controller

And from the older, working BizHawk versions:

joy device: 9ecb8270-4352-11ed-8001-444553540000 `MAYFLASH GameCube Controller Adapter`
joy device: 9ecd5730-4352-11ed-8009-444553540000 `MAYFLASH GameCube Controller Adapter`
joy device: 9ecd7e40-4352-11ed-800a-444553540000 `MAYFLASH GameCube Controller Adapter`
joy device: 9ecda550-4352-11ed-800b-444553540000 `MAYFLASH GameCube Controller Adapter`
joy device: 9ecb8270-4352-11ed-8001-444553540000 `MAYFLASH GameCube Controller Adapter`
joy device: 9ecd5730-4352-11ed-8009-444553540000 `MAYFLASH GameCube Controller Adapter`
joy device: 9ecd7e40-4352-11ed-800a-444553540000 `MAYFLASH GameCube Controller Adapter`
joy device: 9ecda550-4352-11ed-800b-444553540000 `MAYFLASH GameCube Controller Adapter`

Host env.

Broken:

• BizHawk 2.11.1; Win10 IoT Enterprise LTSC; AMD/NVIDIA
• BizHawk 2.11
• BizHawk 2.10

Working:

• BizHawk 2.9.1
• BizHawk 2.8
• BizHawk 2.7

Reproduce the trigger mapping with the Mayflash GameCube adapter on BizHawk 2.9.1 and 2.10+, comparing the reported J1 B5/J1 B6 inputs with X4 LeftTrigger/X4 RightTrigger and the SDL log output. Done means the original controller's digital L and R trigger presses respond reliably in configuration and games on current BizHawk versions.