Invalid Character During Find Operation

Hello All,
I am encountering an issue where I send a file (for example) named send_to_partner.xml and drop off to partners /In folder. I then go to the /Out folder to get a response with the same name I used in sending, but my issue is that in the /Out folder, there are additional characters that precede the file name such as "4 ". That is a four and a space that precedes the file name. So, step 1 is where I do a Find * for any file name. It shows that it found the file name I sent with the "4 " in front. But the next step is where I do a copy/move and this fails with the error “Error executing Copy from Out folder. Error FTP Error! Expected 150 but got 550 The system cannot find the file specified.”
The partner who maintains the FTP site says there is no "4 " in the folder. Active Transfer shows a "4 ".