Soldering the USB port with the stick in it would only partially solve the problem, since half of it is caused by the legs of the encoder, which go in later.
On the subject of that cable, is it supposed to show up as anything on the host side when you plug the usb cable in ?
And halfway through writing this post I thought of putting the jumper on j3, and it does show up in dfu mode, so at least the wiring is good.