Xbox Wireless Controller - analog axes suddenly not working any more

[MikeH]

I was using a Xbox Wireless Controller for KSP on Mac OS 10.12 (Sierra), working perfectly well. Now all of a sudden the analog stick axes don't work any more (buttons are still fine).

Steps to reproduce:
- Connect Xbox Wireless Controller via Bluetooth
- Start KSP
- Go to Settings/Input/Flight
- Click on the Pitch Axis "Primary" button
- Move the left vertical analog stick on the controller
- KSP displays: "Current Assignment: Joy0.1"
- Click "Accept"

Expected behavior:
- Button next to "Primary" says "Joy0.1", clicking it again says "Current Assignment: Joy0.1", joystick works in game

Actual behavior:
- Button next to "Primary" is empty, clicking it again says "Current Assignment: None", joystick does not work in game

Additional information:
- KSP version 1.4.4.2215 (OSXPlayer), tested with locale en-us and de-de.
- Fresh install via Steam, no mods
- Controller is connected before starting KSP
- This has been working last week, and I don't think Steam updated KSP in the meantime, but I'm not sure... I didn't do anything, I swear! ;-)
- No exceptions are logged in KSP.log or Player.log
- The following section does get added to settings.cfg (looks correct to me):

Quote

AXIS_PITCH
{
    PRIMARY
    {
        name = Unknown Xbox Wireless Controller
        axis = 1
        inv = False
        sensitivity = 1
        deadzone = 0.0500000007
        scale = 1
        group = 0
        modeMask = -1
    }
    SECONDARY
    {
        name = None
        axis = -1
        inv = False
        sensitivity = 1
        deadzone = 0.0500000007
        scale = 1
        group = 0
        modeMask = -1
    }
}

- I verified in Unity 2017.3.0f1 with Input.GetJoystickNames() that "Unknown Xbox Wireless Controller" is in fact the correct name, and I can read the controller's analog sticks with a simple Unity test program.
- I tried deleting settings.cfg, complete reinstall of Steam and KSP, reboot, disconnect and reconnect controller.
- I started KSP without Steam by running "LC_ALL=en_US ~/Library/Application Support/Steam/steamapps/common/Kerbal Space Program/KSP.app/Contents/MacOS/KSP" in a terminal to make sure that Steam's controller emulation does not get in the way.

Any suggestions what else I could try to make it work again?

Thanks
Michael