I had two dog leashes fray near the connector that joins the Flat lead to the rope that enters the retraction unit.

In fact one of them was down to a single thread and this one was easy to repair. All I had to do was push the rope through the connector and reroute it through the flat leash and connector and tie a knot in it.

The second one was different in that the section where it would be routed and tied off was on the side and was sealed with a plug that I was unable to remove.

I designed a replacement connector based on the first design and it worked perfectly on the first try.