Notifications out of sync

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I have a filter to notify me about pet sits in Spain.

I am almost always next to the phone and I have notice that I get a notification about a pet sit in Spain and check and there is nothing new.

And maybe an hour later I checked randomly and I see a couple of sits that I have missed and never got notified about.

What is the explanation for this.

It feels that notifications and sits are out of sync.

This has now been reported to tech support.