As a reasonably regular user of Clarkson station, I've been expecting an incident of this nature for some time. When trains leave Nowergup depot in quick succession in the early morning, it appears to be common practice for an empty train to pull in close behind one that is in the platform loading.
I would question why this is necessary. Obviously the signalling will allow it, but the closest together any departures are timed is 3 minutes. This leaves ample time for one train to clear the platform before the next arrives. It's all very well to blame rail surface contamination but the whole issue could be avoided if there was a bit more separation maintained between trains.
I've also noticed similar practices at Whitfords in the past. It would be interesting to know if this is the way the automatic route setting is designed or whether it requires some manual input in the control room to allow entry into an occupied platform.
It was certainly interesting to see what appeared to be a 7 car train when I got off the bus this morning!