That's a 10 minute fix at most, after you find the issue. Cut the wire(s) at the bad spot, slide shrink wrap on, strip the wire ends, solder them, slide the shrink over and heat it, bend the other wires to take up the now extra lenght, wrap all the wires in that part of the harness a bit, stick it all back in the sheath and you're done.
Also, check the the ground wires in the light bulb housings. It will cause that or the turn signals to work intermittently or brake/tail lamp issues. It's very common for them to be loose. I found that most of mine were loose. All you need to do is tighten then screws the ground wire attaches to.