I am not sure if this is a known problem but when the Module prefix is set to ROOT and the Polymer module is added, quite a few files need to be tweaked to get it to work.
To repro, create a new project, change the Module prefix to root then add the Polmer module. Run the project and you can see that for starters the dev url is http://localhost:8080/ROOT-front which will 404.
My project is working but I am documenting this for others so they know what manual tweaking is required to make it work. Or at least how I wanted it to work … I might have tackled this the wrong way?
The following files were changed: