Okay I'd say the more important point here is to get the form in check than if it was a competition OK lift.
Shoulders in front of bar - way in front. I think it's why you had trouble getting your PC to complete the lift over your quads (why your knees went for lockout first).
Big lift will have a bit of rounded back, but you should try to get shoulders over bar, lower back arched, upper back straightish then kinda pull into your body rather than up.
I think if you focus on pulling 'in' and completing with the PC it'll make it easier to keep the bar moving in a straight line.
Maybe a better camera angle might show me to be wrong though, but it seems to make sense to me as to why you had a hard time locking out.