Personally I think the Arnautovic one is an error with his technique which has been coming for a while.
Although you're right that it moves, the best keepers would be standing tall and looking to catch or downpalm that, meaning that even if you can't catch it you're still blocking it. He has a habit of not looking to catch anything like that though, his instinct is to push things away, which means as he was only planning to get his hands behind it anyway, the movement has taken it totally past him. He's been good this season, but not great. Those 2 yesterday were absolute shockers though.
Agree on the standing punching technique.
That's another he needs to get shut of.