Just a thought
This idea may be a result of me learning to fly doing oval circuits on an RAF airfield, but the trace shows the circuit traffic a long way from the runway. That's such a big circuit that they are outside the ATZ.
I'm not suggesting it is causal, but I am wondering if it is normal for you guys to fly such big wide & long circuits. I can normally manage to pfl from 800feet (QFE) on the downwind leg, but I don't see that working from a couple of miles away.
I can see how the ADC might have initially expected them both to be on the Runway before the calibrator got close.