In my limited experience if something is going to cause problems it will be located in a location that isn't ideal for remedy. I'm not sure how inanimate objects manage to do this but in my world they do.
I have a turnout (switch) on the RR that passed inspection with flying colors multiple times when an E8 diesel went through multiple times. It's on the "upper" level near the doorway. So it was time to try a steam loco. WAnt to guess what happened?
That's right, the pilot truck wheel would SOMETIMES jump. And backing the train to try again caused the wheel to get back on the rails but where freight cars (backed) went on top the temporary scenery that goes across the doorway I'd have derailments too.
So I pulled out my construction platform (rathern than stand on stools and small ladders I built a larger platform that I'm not as prone to fall from. (Been there, done that)
After inspection I decided that some rails needed realignment and adjustment. The variances were in thousandths of an inch. And naturally some work required rail removal and some ties suffered damage and needed replacing.
Hours later the track in question was back in place. Repeated testing revealed that most problems were eliminated except for one. Rather than rip a section of rail out once more I decided that I "might" be able to solder a shim of brass to the side ofg a rail top. I've never seen anyone attempt this solution but what the heck.
So I cut a small piece of brass. It is about .006 inches thick .1 inches long and .03 inches wide. Yeah, small.I actually made it longer so that I could bend a section so that I could hold it in location. I cleaned the rail top. I tinned the brass. After much fidgeting I got the brass in approximate location and soldered.
Repeated testing seems to indicate that this repair was successful. I haven't had a pilot wheel jump into derailment, yet. My fingers are permanently crossed.
Anyone want to bet that the brass piece breaks loose 5 seconds before a visitor stands in that location. It will happen just in time to cause a derailment so I can say, "I'm still trying to get the track, just right."
I'd take a picture of the spot but don't think it will show the brass piece.
Little things matter.