It's a known engine limitation that save and load will break winch/plug connections - but not only do the connections break, they render the winch unusable.

After save and load the cable is flying free and generally swings around. If the winch is approeached on EVA and the context menu used to try to plug the cable it won't plug because it's reported as not grabbed. If a kerbonaut approaches the end of the (usually wildly swinging) cable on EVA and tries to grab the plug end with 'y' or context menu it grabs for an instant, then lets go and resumes wildly swinging. It doesn't stay held onto like normal, so you can't return it to the winch.

Nor can the winch cable be retracted to recover use of the winch, as the in-vehicle context menu reports the winch as already at 0m extension.

To recover use of the winch it must be detached with a tool and put in a backpack, then re-attached. This resets the winch's state and allows normal use to resume.

Closing, this actually duplicates #147