goto SE91, enter the message class ZDTB_POR 018 and click edit.
in the next screen select the message and click long text button. from there you should translate this messge into its correct content.
it got probably maintained in english by copy of another message, . the copy process copies all text of available translations to the target message. If it is then missed to care about the other languages, then you get different content for the same message in different logon languages