Yes, it's a new condition I have found since moving to Windows Server 2016 from WS 2012. I've needed to have that trailing slash which could be required due to creating Friendly URLs.
What's odd is that I needed to add the leading slash to peg the file location to the root directory. In the case your referencing, it's only working when that is NOT the case. Very odd.
Thanks for taking the time to look at this Ray.