Quote - Here's what I mean. I put your displacement map and just a Reflect node on. (I have a 3D environment photo around the train.)

I increased the Raybias on the Reflect node to 5 inches. This means it will ignore any self-reflections within 5 inches of the original reflection point. Now on this model, the cylinder cannot reflect itself without displacement. However, with displacement, it seems to be confused about what part sticks out where. Increasing the Raybias made it less confused.

I'm confused about the cylinder reflecting itself.  What do you mean?  I see the black artifacts, but the areas around the bolts look good.  Should I cut a line in each side of each band around the boiler?