Windows does NOT treat long filenames the same across Windows versions

(underneath, there is the old 8.3 name. open a command prompt: type DIR /X *.* to see the linking to the 8.3 names ).
IMHO do the copy with the Higher Version of Windows (Pull the copy from the older system, rather than Push it to the newer system).

If that can't be done.
Open a command prompt and use the XCOPY command