As a test I created a directory D:\Test_1 and put a text file inside. Then tried File.Copy("D:\Test_1\Test.txt","",File.DirTemp,"Test.txt") (which is basically what the packager does with the file)
It failed with file not found exception even though Log(File.Exists("D:\Test_1\Test.txt","")) returns true..
Did the same with: D:\Test1 put a text file in it and tried File.Copy("D:\Test1\Test.txt","",File.DirTemp,"Test.txt") and it works.
I can only think that it is something to do with the underscore in the folder name. It does seem strange, but as I have never used them, I hadn't come across this before.
Someone else may have more insight.