\\<server>/Data/DATA_DIR/INBOUND/TESTMD5/TESTFILE4.txt
I suspect that it is the mixed backslashes and forward slashes and/or angle brackets that the OS doesn't like.
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.