I've pulled my hair out over this.  I think this picture is cursed.  First the Poser file got corrupted and wouldn't render anymore.  Ok...so I remade it...but every time this rail set I have does this.....I have no idea what causes that....is it a setting?  Is it just a badly made item?  

I also tried a different product that I had used before with no problems and got weird warpiness!  The square platform was all wavy...

I tried googling it, but no luck.  

I would attach my render settings, but it won't let me put more than 1 picture.  These are the same render settings I use for everything else....

Thank you!