Given that the issue with notifications in Discussions still isn't fixed, could you verify whether or not the information from ticket #1093556 was passed on to the team (or if they have already figured that out)?
It issue is triggered by specific types of notifications. So if you never get those types, then you will never have the issue. On the other hand, if you always get those types, then you will always have the issue. Most people get these specific types from time to time (with varying frequency) so the issue appears to "come and go".