WebDav appears unsupported?

Hi 
I have purchased SmartFTP Ultimate which is supposed to support WebDav. I am able to make connections and upload to our server using ftp however I cannot download files from our server. 
Files download as 1kB size only, and then go into a cycle of retries. Filesize mismatch errors occur.
 
Can anyone please assist.
thankyou
 

Please contact support: Menu: Help->Request Support and provide a test account for the server.

Unfortunately I am unable to provide server details as this is a corporate site. Also we have not subscribed to paid support.
There are many forum entries regarding Files download as 1kB size only, and then go into a cycle of retries. Filesize mismatch errors occur. for other protocols also but SmartFTP does not not appear to provide suggested solutions.

The other forum posts you may have found are unrelated to your problem. Your support plan is active, please contact us through menu: Help->Request support and send the logs from the transfer queue item: double click the file in the transfer queue.