No, it's the many marks he drops when an opponent touches him even slightly. It is an area he needs major work in imo.
I think those marks stand out too much because he is such a big man and we give him little credit and expect a lot of him in the contest
In the Hawthorn game he took 3 marks inside the 50, one he stood in front as a pack formed and was just too big despite a pack jumping around him. One other he jumped above Fas and Sicily and took them out of the contest and the other he ran back and jumped over Fas and Birchall giving Birchall no chance to spoil given Cox's size. Only the pack mark was rated contested. My point is all these marks involved some degree of contact and increasingly, albeit incrementally, he is better with contact. I dont think this problem is as major as you feel it is.
The other area which makes me feel he is progressing is the VFL numbers he put up this year
He has 5 games
Round 1 6 marks 4 contested
Round 5 8 marks 1 contested
Round 7 7 marks 5 contested
Round 8 5 marks 3 contested
Round 10 15 marks 4 contested
Averages 8.2 marks per game. 3.4 contested marks per game.
I am not saying he will clearly make it and on Saturday he was disappointing. Still there is improvement and the physical side of the game is improving. He is still very green. How much he improves I don't know but but I dont think he is as fragile with touch as he was in 2016.