I think I have found the problem. If you export the *=Default templates and then import them leaving the the name as default and then export a distribution package and then import it, it appears that you not only get multiple entries in the distribution package(s) but also in the return code manager and you lose the ability to assign the templates. Renaming the imported template and then going into the distribution package(s) and assigning back the the *=Default seems to allow you to be able to clean up the multiples.
Sounds like a bug to me.
This is being worked on and will hopefully be fixed in an upcoming SP.