When someone is mentioned @ by another member, the person that was mentioned will receive a notification but when clicked on it wont lead to the relevant thread but to the main wall of their group. The issue refers to public mentions, e.g. on a wall.
It seems that it works as it should for example in private chats. e.g. if mentioned in the chat connected to a specific activity
Turns out we already had this on the board, as Bell notification for @-mention does not bring you to the message