REPLACE channel fader error

Replaces the channel faders, soldered 3,1,2,4 and only gives the 3, the others do not raise or lower the volume, tested the tensions and everything is fine, is there any configuration that has to be done ?? !!

Have exactly the same problem changed 312 faders now only 3 works how did you sort this out did

It must be cheaper to make a mixer with faders soldered straight hard onto the mixer main board, I can understand that.

But really wouldn’t our customer or owner experience be better for us and the resale value if all mixers and all in one models had users-replaceable faders that could be change from the top of the mixer.