If you can arch more, great, but at least youre keeping your back angle constant. The reason why youre missing is because youre not over the bar enough. Your shoulders are in line with the bar so that means you have to extend back on your extension to bring the bar to you resulting in either 1) catching it fwd, or 2) looping it from the behind.You look more over the bar in your first vid, but the reason youre missing there is that youre not pushing your knees back enough from the start. The bar is travelling around your knees so its going to get bounced out when you brush it. You try to compensate by hopping fwd slightly, but thats a hard skill to pin down...harder than learning to push your knees back when you start the lift.