Id bet its more of a personality issue.
I was a Walstud fan at the draft. I doubt his issues are technique or technical. He is SOUND in those departments. The defination of textbook technique goalie.
On the other hand i was really impressed by Cossas personality after being drafted. He is smart, charismatic, and confident. Shades of Seider.
SY made it apparent he was gunning for key players with strong character to be the bed rock of this new era. Id bet Cossas personality set him apart - whereas walnuts likely had the same boring stoic personality of every other blue collar swede.