Using newest 6.1.5 build.
Within .net task, when opening file for write access and use UNC path "\\server\dir1\dir2\file.txt", It returns permission error. When I use mapped drive "I:\dir2\file.txt" it works fine.
Are you using a Credential?
I am using the same credential for both tests.
Does it work with Credential and UNC path if you remove the mapped drive? (it sounds like some kind of conflict)