this is classic AI / stable diffusion, it tend to read not the lines as lines but as an alignment of pixels and therefore not necessary super straight.
as Endlessfixmentions here
it’s not a clean render tool, it’s a tool that will make a snapshot of your 3d and try to interpret it.
lines, in pixels, are not straight, they are aliased (the small pixel stairs), and they maye lines technically wavy.