I have no idea which mod is breaking it, but when this one and Train Construction site ( https://mods.factorio.com/mod/trainConstructionSite ) are both installed, the latter is broken, as you can't build a trainbuilder then. It simply says it needs to be built on a rail, even though a rail is placed.

I've also posted this on the other mod's discussion.

I was going through the github code to see if I could deduce somehow what the problem was, when I saw you made a commit and then saw you made a new version. I just checked, and the new version seems to fix the Train Construction Site.

Thanks for this! :)

well... glad it helps :)