Did you happen to notice if that track joint was hot to the touch when it was "shorting". It is possible to have a "high resistance joint" which may cause the problem you described. Sounds like you found and corrected it.
I've never come across K-line super snap track, though I have heard of it. Does it have metal ties and fiber insulators like classic tubular track? The reason I ask is, if it does, another possibility is a punctured insulator.
Years ago I bought brand new Lionel O gauge track, and was having shorting problems all the time. I'd keep taking the layout apart and isolating the short to different sections. Eventually, I figured it out, and each time I would loosen the tabs a little and it would test OK after that
