Only one message is having this problem or more?

If any user delete that message from front-end then this error occur. If “Members” group have 5 recipients and one of them deleted that message from front-end (From “Message Box” user can delete any message for himself using bulk action) then all other user will see this error.

This is a feature so that if any user delete a message and other user reply to that message then who delete that message will never receive that reply but who replied will not know if that user receive that reply or not. He may think that deleted recipient is ignoring him. So we made this so that if any user delete any message other users cannot reply that message anymore.