Maybe some of you met this kind of problems which said the modification time of files on FTP server were not set properly or related information of it were reported during runtime after configuring the FTP Adapter. Even though the time format was correct through verified with the file system listing command: quote mdtm filename. But it would be the problem of time zone either.
To solve this problem, the easiest way is to erase these below properties: FileModificationTime and ModificationTimeFormat from the FTP Adapter wsdl file.
Then test it and it will work correctly.