Can't assemble train

https://preview.redd.it/7689pmbxx9hf1.png?width=2553&format=png&auto=webp&s=fe75f0172cb6c334c5b5756a9f9e95a408ca45e1

Not sure what this is meaning, I tried moving the bogey around. No matter where I put it, it shows this message (and the coordinates of where I put the bogey)