Re: Host is not communicating for more than 15 seconds. Still waiting...
Please post session log files both from working and failing session.
To generate the session log file, use
/log=C:\path\to\winscp.log command-line argument. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.