I think your phone doesn't have a localized (language-specific) string to display for whatever message it wants to show there.
Have you by chance updated phone loads without a CM devpack, or otherwise gotten into a situation where the phone wants to display something that isn't supported by the server-installed locales?
Somehow the phone was stuck with DND on but wasn't displaying this, after
replacing the phone with a new one, the three ??? when away and all is back to nor
mal. Thanks for the info.