... figure out what made it so tipsy.
Maybe it was still celebrating the fourth.

Serious, some times there is no logical explanation. Some years ago I was asked to show my H0 layout as part of the home tours for an NMRA meet. It was my first time, so I wanted everything to go perfectly. I ran the trains for about 20 hours before the show and for the 6 hours of the show without a single derailment. Right at the end, the show chairman brought Jim Hediger, senior editor of Model Railroader, into my train room. You know what's coming next, and it did. One train went over on its side, locomotive, all the cars and the caboose, one at a time and very neatly. No reason for it, it just did.
Jim