Controller issue with Superflight (732430)

Compatibility Report

• Name of the game with compatibility issues: Superflight
• Steam AppID of the game: 732430

System Information

• GPU: GTX 960
• Driver/LLVM version: nvidia 396-54.1
• Kernel version: 4.18
• Link to full system information report as Gist: Gist
• Proton version: 3.16-3

I confirm:

• that I haven't found an existing compatibility report for this game.
• that I have checked whether there are updates for my system available.

Symptoms

When I play the game with my wired xbox360 controller plugged, the game is unplayable. It's like if the right direction is always pressed. It seems also that even the up direction is also pressed a little, but not to the max. Without the gamepad, the game is perfectly playable with the keyboard.

Even navigating in the menus is complicated if the controller is plugged.

I've tried on windows and I don't have any problem with the same computer. So, it may be a proton issue.

I've tried rebooting my computer but it did not changed anything.

It's not just a problem of deadzone because even if I press my stick on the other direction, it doesn't change anything.

I've played tens of games with my gamepad with proton or native linux games and I haven't any problem.

I've even tried using "LC_ALL=C" in the command line since I'm French and there is sometimes a problem with decimal numbers in Unity games if this is not set. But it didn't changed anything either.

Reproduction

Just launch the game with a controller wired.

No source file, test, or entry point is identified in the report. Start by reproducing Superflight with a wired Xbox 360 controller under Proton 3.16-3 and investigate the controller-input path; done means the game and menus no longer receive constant right or up input.