Cause, no one uses mapped drives any more, amirite?
There's absolutely no reason to use mapped drives in this day and age.
But it's one of a few ridiculous issues in 1803 and 1809, my favourite is the file association mechanism being broken in some cases, for example I like to have .TXT and .CSV open with Notepad++ (what lunatic would use Excel for CSV files?) but 1803 says noooo ...