At Banbury show, the J50 locomotive was giving us grief. I've always had "fun & games" with compensated chassis based models which in my experience only run happily when pointing in a particular direction*, but this time it was different. Every time the loco reached the station the model lumped off the track.
After running it back and forth a bit, the problem became apparent, the side steps were just clipping the side. As the model reached the end of the platform, it was jacked up on one side thanks to the ramp, until it stopped or fell off. Or both.
So, despite all the effort I put in to build a model like this, I'm not adverse to doing horrid in-service modifications. Initially the steps were bent out of the way which seemed to help. A more permanent fix was to trip a fraction of a millimetre from the end of the treads with some scissors. OK, so it's still not engineering but it did the job.
Of course if I was clever I would have wondered how an etched brass model railway engine can put on weight. It's not like we feed them or anything after all, yet the model had previously been through the platform road without incident, and the platform hasn't moved either.
In fact when I looked properly, the loco body was on the chassis wonky. Looking down the layout this was obvious. Undoing a retaining bolt and tweaking gave me plenty of clearance. As long as the model was pointing in the correct direction anyway.
*This is probably 'cos I'm rubbish at flexi-chassis building.