FWIW, I have abandoned this plugin. We had an issue with even 1.503 (we're still on 1.503) where I could not deploy/connect to a particular Windows box no matter what I did, when smbclient had no problems at all. So, I resorted to using:
smbclient -E -A ~/.cifs_credentials "$SHARE" -c 'prompt; recurse; mput mydir' 1>/dev/null
While not as flexible as the CIFS plugin, it works. But, smbclient does not return an error if this command line fails (so the jenkins job succeeds). I have found no good way to make smbclient fail whenever there is a problem (like invalid credentials). One way I found to check for this is to try to put a file as a simple check (without mput):
echo "xts-$BUILD_NUMBER" > xts.build
smbclient -E -A ~/.cifs_credentials "$SHARE" -c 'put xts.build' 1>/dev/null
... continue with actual smbclient copy...
This fails under a few tests I performed as I had hoped, but not all.
SHARE is //system/share type share.