I believe that the pins in this picture #3 (the close up of the wires on their pins , is backwards) You can even see in the ifixit picture that the label says main but the pin says auxiliary!!

Please can someone check??

When reinstalling: , the wires connect as :

WLAN MAIN ANTENNA WIRE (GREY COLOR ON MY X1G6) goes to the MAIN PIN - (labelled as #2)

The other wire (which is black), and is labelled as WLAN AUX, goes to AUX pin (Labelled as #1)

These colors appear different to the pictures above, but ignore the colors if confused- just do: main to main, aux to aux.

Agree with both comments above: lift from top left and top right of battery. This disconnects it and it lifts out and away.

I had to use a PH1.