In all the years I have worked on the layout I never had this happen…
Today I am lowering a trestle on one end by about an inch along with about 10 feet of track. If a train is pulling uphill it’s fine but if it’s descending it sometimes derails.
I am digging under the trestle to lower it and happened to look at one side only to see a ground squirrel looking back! He was about six inches from my leg and apparently comes under the trestle when he’s headed for the pine trees. I think he was as startled as I was!