Headphone works on 1 side only

Hi @mees89059

Start by reconnecting the broken wire and then test the headphones to see if there are more problems or not.

You need to strip a small length of insulation off the loose white wire and resolder the wire onto the FB_LP terminal on the board.

If the wire won't reach or there's too much tension on the wire if it just reaches, splice in a new piece of wire between the broken wire and the FB_LP terminal. Make sure that the joints are insulated

Here's a zoomed in image of the image you posted showing where to connect it to.

Be careful when stripping the insulation off the wire as you don't want to break the wire when doing so.

Not totally sure but perhaps FB= Feedback and it may be used to aid any noise cancelling that may be used by the headphones.

(click on image)