Would either of you mind trying two things just so I can report it properly?
1) is it still happening to you now?
2) If you click on view all instead of the alert flag, does it take you to your list of alerts?
Sorry to ask you this, but when I can't recreate an error myself, it's hard to explain to support.
Of course, whenever you try to upgrade your site to make it better you get side issues like this which we haven't seen in many months. Our apologies about this, but I hope you'll agree with some of the new functionality it's all worth it!
It appears there is an issue with the new addon and one of the ones we had before. I have turned off our "old addon" for now, as that one just allows likes for private conversations, and the ability to sort Pm's. So those two features will not be working for now until we sort out. But the error messages have stopped. Let me know if anyone gets another one after this please. @Purl@Sunshadow@Ripley