Is probably not a major bug, but it is something that I don’t think should be happening. I’ll give a photographic example:
Here is my sandbox car that has 1988 for both model and trim, and as you can see it has Steel, Galvanised Steel, Corrosion Res. Steel and Carbon Fibre for the chassis materals.
And this is my car with the trim set for 1992. The AHS Steel option for the chassis has appeared but in selecting it, the car enters a perpetual loading state until an option that is available for the model year is selected instead.
As I said before, it is not a major bug but just a weird interaction within the sandbox that probably hasn’t been noted because not many people would make a facelifted trim without any other trims existing. If it’s not deemed problematic enough to deal with then this can just be left here to show that if anyone is having issues with selecting the chassis materials then this might be a potential reason as to why.