If that's happening, it's because people are bailing out of their heavier lifts too early, i.e. letting the knees slide forward because they can't maintain their position over the bar long enough - so it's not an actual DKB.
This is actually happening with you a little bit. when you get the bar past your knees, keep pushing them and your hips back as you extend the knees - this will keep your shoulders just bit forward of the bar. Right now you're almost sitting behind it as you stand up, which is why the DKB is tough to see - your knees never come back very far.
Relax your arms - looks like your elbows are locked right out of the gate.
Flare your knees to the sides in your start position and 1st pull - those long ass legs are in your way.
On some of those attempts you pulled early with your arms - likely because of your weight balance and extended position. Your weight is a little forward on your feet, and you finish completely vertical - get that weight back on your heels once the bar leaves the floor and get just a slight layback at the top position. If you're extending vertically, your weight has to be forward, and if your weight is forward, you're going to naturally want to bend your arms to rush the pull and get back in balance. This is also why you're jumping forward and why the bar isn't quite stable overhead.
You're getting some weird neck/shrug action - hard to see in that video, but it looks like you're actually shrugging before you finish extending - and when you do finish, your really over extending your neck. Try to keep the neck approximately in line with the body (so it will be leaned back slightly at the top) - and remember that you only shrug to pull yourself DOWN once you've finished driving all the way to the top with the legs.
Your squat stance looks too narrow and too straight forward. Looks like you have some pretty long legs - widen up that stance a bit and turn the feet/knees out - give yourself some space to get down low.
You need to be way more aggressive with the 3rd pull - turn that bar over as hard as possible and drive up on it - imagine receiving it overhead at the same time your feet reconnect with the platform.
All that said, however, you actually look pretty good. Keep working and keep watching videos of yourself and comparing them to competitive lifters.