DW MX & Contribute

Just wondering whether anyone can comment on this ftp log
from trying to get my copy of DW MX to administer / set up Contribute fucntionality on a site
(server passes tests with the adobe downloadable ftp testing tool)
server ftp software is pure_FTPd [TLS]
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RNFR /public_html/TMP6bmtwd10j2.htm
350 RNFR accepted - file exists, ready for destination
RNTO /public_html/DWDDXX7.DDD
250 File successfully renamed or moved
DELE /public_html/DWDDXX7.DDD
250 Deleted /public_html/DWDDXX7.DDD
RNFR /public_html/DWDDXX7.DDD
550 Sorry, but that file doesn't exist
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ie DW has just deleted the file /public_html/DWDDXX7.DDD
and then it asks to rename it from /public_html/DWDDXX7.DDD
and of course it doesn't exist
and of course there is a resultant fail message on the Admin screen

- so why is DW asking it to rename a file that doesn't exist?