It's time to look for some connection to the mainboard
Some time ago i took some pix of some parts of the board, that could be of interest.
Deleted the pic.
Please stay tuned for an update
Shows the audio jack of X1.
The switch contact is known to cause the "stick to headset mode" errors
This is one important subsystems on X1 mainboard.
Handles keyboard and similar things...
I2C communication is also used for this chip!