Dolphin emulator: Nunchuck stuck in forward right direction

I have Super Mario Galaxy 2 in the Dolphin Emulator. Since I have to point for certain things and use the joystick on the nunchuck for general movement (and I don't have a USB sensor bar), I want to play with the nunchuck in my left hand and the computer mouse in my right hand, while the Wiimote just lies around (because I don't have a third hand).

This works fine (except for shaking, but that's a different question), but the Nunchuck joystick is apparently stuck at the top right, because Mario keeps walking in that direction. I can make him strafe a bit to the left or right using the joystick, but the overall direction stays the same.

Interestingly, if I click Movie->Start recording input, he doesn't do that anymore, but Mario keeps ducking and no input from the real Wiimote or nunchuck are accepted anymore. And apparently I can't turn recording off again by any other way than closing the game.

I tried separating the Nunchuck and reconnecting it to the Wiimote while playing, while in the home screen, while the game is not running, before connecting it to my PC, etc., but it doesn't help. I even tried holding it to the top right while connecting it to see if Mario stands still at the default position, but that changed nothing.

Setup:
American version of Super Mario Galaxy 2 (SB401?)
Dolphin 5.0 (ac267a29405ae768037a8774b84b805a4180d1af)
Windows 7 Professional 64bit +SP1

How do I stop this? If it's possible to just fix the "Start recording" behaviour, that would also be ok, although inconvenient, because I would have to click it every time I start the game.

(Possibly related question)