5mm is not a lot indeed.
Maybe You can cut it at where it broke, and then strip the insulation off the last 5mm, open all the strings and then wedge an piece of 10 gauge wire in it?
And then offcourse solder it.
Like done here:
https://www.youtube.com/watch?v=bOk4yqaSPJM
Hope it helps you!
Ruud