Hello Marty,
Thank you for your suggestions.
I found when configuring a host to use Custom Server Security, the capitalization of the username matters. For example, logging on with username "johndoe" will fail if the username on the server is "JohnDoe".
If case-sensitivity is by design, more clarity is needed through the documentation and app dialogues to remind users.
Yes, it is by design. We will mention that in the documentation and possibly also in the interface itself. Alternatively, we will consider following the Windows scheme instead.
Unsuccessful logons should be prefixed by something more meaningful, eg "RU Server Authorization Failed"
Yes, this is a known issue. We will add a message in case of a failed logon attempt.