Astir8,
ouch, had totally forgotten about these ones. Beside a broken cable, the pull-out car driver not keeping a steady speed and pulling out the cable at about the same speed the drums deliver them was a frequent cause of such a mess. Much cursing ensued; more than once I have had to take the chisel, simply cut the knot up in order to untie it and then resplice the cable - this was sometimes the fastest method to unjam the cable. It was most fun during thermal season with all the cross-country guys waiting over at the launch pad, the phone keeping ringing every 4 seconds ("Are you done yet?" - "NO!" (SLAM!)) and the flight instructor coming over to berate You for taking so long, but then at least lending a hand.
At my club, everyone wanting to fly plastic gliders had to get the winch license and got half a day on the winch about once every 4 to 6 weeks. Procedures at other fields were different.
A nice thread btw - the winch driver is an oft forgotten hermit at the far end of the field.