macOS, Can't disable default calendar alerts I've been having this problem for probably about a year now, and I have no idea why.

I like having a default calendar alert, and I do use them.  However for many of my repeating calendar events, I don't want the default alert, instead wanting only to be notified at the time of the event, for example.

So on those events, I change the default alert value to "none", and when prompted if I want to save for all future events, I say yes.

If I then edit the event, I can confirm visually that the alert has been changed.  I can quit Calendar, re-open it, and again confirm that the former default alert is now set to "none".

But then if the event is more than a couple of hours away (like the next day for instance), the default alert will be back.  For all future events.

I do use iCloud calendars between my iMac (macOS Sierra), Macbook (High Sierra), and iPhone (iOS 11.3), and it doesn't matter which device I make the change on, it will always revert.

This is seriously annoying, does anyone know why this happens and how to fix it?
UPDATE:  Cancel all of this.  I just realized today that all my default 1-hour alerts are again back on my desktop device calendars.  However they are NOT back on my iPhone.  iOS shows no default 1-hour alert, but macOS does on both laptop and desktop (High Sierra and Sierra, respectively).
So I don't know if this is a bug in macOS Calendar or iCloud or what, but it's still driving me nuts.  Original "answer" follows.

At the moment it appears I have finally solved this.  Apparently I must not have tried changing all the alerts from my phone after all though I thought I had.  Changing them from macOS simply did not work, but changing them all one by one from the phone, seems to have done the trick.  This morning my usual alert at 9am that always would go off at 8am, did not.  It went off at 9am as desired.  So unless I find things revert back again... I'm going to call this the solution.

Change the alerts from an iOS device, not macOS.