Way back when I had a customer pay one of his employees to fix a broken wire on the cadence sensor mounted to his tandem. Each strand had to be soldered together. Not sure why, however it took the guy over an hour to do it. The point is, anything can be repaired provided time and skill level are available. Now, is it worth paying shop rate to have someone tear down that wire harness in the shifter to fix it? Likely no.