Shots against the hand can happen, it wasn't in an unnatural position it's just unlucky. It's when you start giving away 15 like Polpo Matti that it becomes a problem.
His big fuck up was when he misread the bounce earlier on and let them in. The "foul" that Salernitana insisted was a penalty (and in typical Italian fashion, according to them was worth the same as a disallowed winner in the 97th minute) was close to a penalty. But tbh Pyontek had already shot, it was very borderline as Bremer was also clumsy there.