iCal - how to stop aletrs of specific shared calendar?

Hello helpful and knowledgeable folks!

A google calendar that was shared with me and is unchecked on iCal (so that I won't see it on my computer) keeps on sending me alerts. From time to time the alerts do stop, and that lasts for a while (several weeks) untill, for no apparent reason, that calendar gets checked somehow and appears again on my computer, and after I uncheck it, I keep on getting the alerts.

Is there a delay between the time of unchecking the calendar and the termination of the alerts?

But even so, why do the unchecked calendars reappear for no reason?

And is there a way to stop alerts for a specific calendar without stopping alerts for ALL calendars?

Thank you!!!