Error: "A subtree cannot specify a different DAV provider than its parent"

I have setup a repository location on our Apache server at '/repos' with the following:

<Location "/repos">
        DAV svn
        SVNParentPath /path/to/repos
        SVNListParentPath on

I did this so that I could simply create new repositories and have them immediately available without having to create new Apache conf files and restarting the daemon. This setup produces repos with URLs like: http://svn.domain.dom/repos/reponame

Sometimes, however, we have need to give external vendors access to a repository or a specific branch of a repository. Since I don't want them to have access to any of the other repos or even to the list of repositories itself, I've been creating additional Apache conf files specifying a different location for the same repository:

<Location /reponame>
        DAV svn
        SVNPath /path/to/repos/reponame

While this works, it produces continuous Apache errors that fill the log and, if unchecked, the drive. The error is:

[Tue Apr 09 14:30:50 2013] [error] A subtree cannot specify a different DAV provider than its parent.

I believe this is related to using "SVNParentPath" for the location in one place and "SVNPath" in another. Is this correct? Or is it the re-specifying of "DAV svn"? Either way, if I remove the two SVN lines from the vendor workaround conf file, SVN stops working.

How can I fix this?

-- 
Remo Del Bello