Currently the backup logic checks if the SSH output contains the string "
password:" or "
Password:" to determine if the remote server is prompting for the password.
This issue occurs if the remote SFTP server being used as the backup destination, returns a string of text after the word "password" followed by the colon in the password prompt when making a SSH connection.
For example the following prompt from a SFTP server would return no match with the search query (password: or Password:), since there are additional strings after the word password, this will be logged as "Unexpected SSH output" message in the logs above:
# Login as: user
# Keyboard-interactive authentication prompts from server:
# password for user: