Emulator

Game Name?
Should apply to all GC games, but only tested with Burnout 2.

What's the problem? Describe what went wrong.
When configuring the Gamecube controller on recent development versions of the emu, attempting to map right shift will map the button to left shift instead. Attempting to use the right shift key while the Gamecube button is mapped to Right Shift will cause that button to not respond.

What steps will reproduce the problem?
Go to Controllers, then configure the Standard Controller in Port 1. The device shown should be Quartz/0/Keyboard & Mouse. Select a button to remap, then press the Right Shift key. The emu will show that Left Shift is mapped there instead.
You can also manually set the button to Right Shift by right-clicking the button to remap. Then, if you go into a game and attempt to use that button, the button presses will not be registered.

Is the issue present in the latest development version? For future reference, please also write down the version number of the latest development version.
Yes, it's present in 5.0-5789

Is the issue present in the latest stable version?
No, 5.0

If the issue isn't present in the latest stable version, which is the first broken version? (You can find the first broken version by bisecting. Windows users can use the tool https://forums.dolphin-emu.org/Thread-green-notice-development-thread-unofficial-dolphin-bisection-tool-for-finding-broken-builds and anyone who is building Dolphin on their own can use git bisect.)
5.0-5341 (clean up OSX input selection)

What are your PC specifications? (CPU, GPU, Operating System, more)
Mac OS 10.12.6 (Sierra)

Is there anything else that can help developers narrow down the issue? (e.g. logs, screenshots,
configuration files, savefiles, savestates)
Even in versions before 5.0-5341, the Quartz keyboard did not correctly register right shift, but the other keyboards (Keyboard/0/Apple Internal Keyboard) worked correctly. However, that version removed these old keyboards.