Last month, some buttons were stuck because my friend was mad drunk and spilt coke on it.
So there are 8 photos how to dismantle buttons to clean and mine works as well after clean up~!
T10 Torx ( you also need T20 when you dismantle iDrive buttons from center console)
toothbrush and warm water (for cleaning stuck parts)
- it depends on you will take off all buttons, but I don't recommend because all buttons (except menu button) look easy break with a snap when I tried. So I highly recommend to take off only menu button.