OK, so I look down and the little metal end cap squeezer thingie has come off the end of the cable on my rear DR, and the cable has unraveled–a lot–way back to where it is pinched by the DR. THIS MUST HAVE HAPPENED IN MY SLEEP BECAUSE I CHECK EVERY COMPONENT ON MY BIKE THREE TIMES A DAY, AS YOU RECOMMEND.
So do I just sort of twist the cable back together, put another little metal end cap squeezer thingie on it, or do I need to re-cable?
Not Demerly, but then again that was hardly a PM 
I say re-cable. But instead of using those POS little crimp ends, dab a little superglue, epoxy, or even solder if your so inclined on 'em. Works much better than those little ends do.
PM meant Preventive (or preventative) Maintenance. I see that might have meant Private Message. Sorry for confusion. Could have meant pre-menstrual, or Prime Minister
I’ve been using the heat shrink electrical tubing trick I learned about here and it works very nicely.
Hmmm, well, here is what I would do here in the store:
Replace the cable the inner cable. When the darn thing gets crushed like that it may slip- a little at a time- through the clamp bolt. Not good. That causes that subtle degradation in shifting.
Murphy’s law dictates that it will slip the entire way through at the worst possible time.
Can’t I sue my LBS owner and his mother and father for not crimping the end cap on properly in the first place. Isn;t everything someone’s fault? What kind of a country is this?