Why is this alert 1:55 minutes late and wrong?

Hey everyone,

I’m seeing an alert in my dashboard that I cannot really explain. The yellow pending line is OK, as it signals a missing “invocation” within 15 minutes after the last. What I don’t understand is the alert that should have fired 15 minutes later (still no invocation at 10:30) but didn’t. It waited for another 1:55 minutes to fire, even though in the meantime (10:30:00 - 10:31:55) an invocation point arrived. So the alert is both late and - due to being late - also wrong.

What is going on here?

Thank you very much!

Oh, additional information: query A is “Invocations”, query B is “Errors”.