What seems to be the bug? Is it the texture on the bolt in the bottom right of the first picture?
PS: Knowing how smart I am, I am probably missing something really obvious.
After reading your post and look at the pictures carefully, I realize that is not a mistake.
For me the bug was a repeat of the texture in the exhaust pipe, but now I understand that repetition is to stimulate this:
About the screw, the distortion is due to the angle of the image is very open / wide.
Yes, the pipe is supposed to have a texture (as far as I know).
In my head that was a rigid pipe so I thought this was a texture bug, I now realize that it is actually a flexible pipe. Quite common in the stands engines.
Solved and locked.