We are still collecting information, but several users of the German-language Wikipedia are reporting that they have not received any Echo notification that one of their articles was linked since end of June. (permalink to current state/live link (will be archived))
The two users who have confirmed they stopped receiving notifications are Hoefler50 and Lómelinde. We are still trying to find out if this affects all users or just a certain group.
Since the change to global preferences falls into this timeframe, it might be that this Echo problem is related.