I recently had all four flights on YYZ-YVR-PVG delayed/cancelled.

AC103 went mech, cancelled, was put on AC100 and overnighted in YVR.

Next day AC25 diverted to ANC due to medical emergency, delayed for 2 hours.

AC26 was delayed by 1 hour due to late inbound, delayed boarding. And my flight to SHA was late by 5 hours, landed only 2 hours before AC26 departure.

AC100 was late for 30 minute due to crew being late. It was switched from A321 to B789 so different crew members were required.

And I recall in another Asia trip, I had all four flights delayed due to de-icing, de-icing, late inbound due to de-icing, waiting for gate at YYZ and frozen aircraft doors.