There are certain types of user input errors, that are known - they’re handled by the server, but the client delivers them wrapped by redundant generic message.
The message “Server error occured…” is basically incorrect, because it is problem of the user. It shouldn’t be shown.
The next type of problematic error message is following:
There are two sentences saying the same thing. The first one is localised and user friendly, while the second one comes from the SQL subsystem. The second one shouldn’t be shown.