That is an interesting behavior that is occurring. I attempted to build out a similar joined table in Tableau Desktop and was unable to reproduce the above behaviors. I am curious what version of Tableau Desktop is being used? I was unable to produce the above with Tableau Desktop 10.3.0. Also, is there a chance the screen shot from the metadata screen could be attached to the post?
I have been using Tableau 10.2. I downloaded 10.3 and had the same result. It did not resolve the issue.