Classic-fit washed cotton poplin shirt in sleepaway stripe

On one side of the shirt is a section of dark navy (serge?) stitching that is very visible — especially on a white background fabric. I assume there was some error made in manufacturing. The actual fabric and everything else is fine, but unfortunately having a dark splotch of thread on one side is hard to hide. I wanted to return, but couldn’t because it was bought on final sale. Very disappointed.