One thing we have learned about creating xrefs is that the path formatting in the map needs to match the formatting of the link.
This would work
map path
Ie \\network_location\here\12345.dita
link path
Ie \\network_location\here\12345.dita
This would not work
map path
Ie ..\network_location\here\12345.dita
link path
Ie \\network_location\here\12345.dita
Bryon