Trip planner API returns RealtimeTripId with no associated GTFS data

Hi - I’ve noticed for some bus routes and train journeys that sometimes the Trip Planner API returns a journey with a RealtimeTripId, but that the associated GTFS source doesn’t have an associated entry.

I’ve seen it for regional buses and Sydney trains. I’m aware that there are multiple regional buses URLs and that the Sydney trains GTFS feed is on v2, but still there are times when this happens.

Is this expected? I understand that some journeys might not have real time positioning for whatever reason, but if that’s the case I’d expect the journey API to not include a RealtimeTripId value…

Thanks,
Andy

A little info addition - I’m also seeing a scenario where a bus making its way to the first stop of its route is sending location info, and then as soon as it gets to the first stop the tracking stops… although the RealtimeTripId remains…