Authentication in Subversion 1.8+

We have a Subversion repository which by default requires authentication
disables all anonymous access, but enables anonymous access for certain
directories. For Subversion 1.6 and 1.7 clients this works fine for
anonymous access. However, when using Subversion 1.8 and 1.9, a request
for the same directory that worked fine under 1.7 requires authentication.
A quick wireshark seems to indicate that during the PROPFIND calls made by
1.8+ clients, the client somehow hits an authenticated path.

Can anyone shed some light on this behavior?

Thanks

-- 
Mark Bidewell
http://www.linkedin.com/in/markbidewell