In 5.9.2 .NET library
If the same Session() is used with multiple SessionOptions() and one of the ScanFingerprint() throws an exception, the e.Message will contain logging from the previous connection.
winscp> option batch on
winscp> option confirm off
winscp> option reconnecttime 120
winscp> open "ftp://xxxxx:xxxxx@xxxxx:21" -passive=1 -timeout=15
Connecting to xxxxx ...
Starting the session...
Active session:  xxxxx@xxxxx
Secure session (SSH or TLS/SSL) not specified.
"Secure session (SSH or TLS/SSL) not specified." is the only information I expected from e.Message. Anything before that is from a different SessionOptions(). Also, if it continues happening it will just keep adding to the e.Message and will end up with multiple "Secure session (SSH or TLS/SSL) not specified."
I haven't been able to replicate it on other methods.
Not sure if a known issue. Just thought I'll let you know about it.