Calendar adds second event alert by itself

How do I stop Calendar from automatically adding a 2nd alert to repeating events? It keeps re-adding the 2nd alert even after I delete the 2nd alert or delete and recreate the event!

I go through and make sure EVERY event has ONE alert, and a day later some events have magically got two alerts again

I’ve gone through my iphone iPad and Mac settings and all are on the same default alert of one.

It’s a mystery

• ok so update, it seems calendar is doing two things, it’s allowing edits to be reneged and it’s not updating future events when I choose it too.

I think this will be something for the call centre to help me with