Leave gaps in the copper. Do not overheat. Just enough to melt solder when you touch it to metal. And do use flux.

Can help to rough up the wire a bit with some sandpaper.

That being said, I have had some good luck with plumber's epoxy, that stuff that somes in rolls. Mix it and roll out thin, less that 1/16. Rough up your wire a bit with sandpaper and wrap loosely with copper. Then wrap your epoxy around and press it in to fit between cracks in your LG wires.

Very strong stuff when it hardens.

Tom