Form check - 5x125kg Deadlift, really inconsistent back rounding.

[Silversonic]

I do 3x5 Deadlifts on Monday and 1x5 Deadlifts on Thursday (the latter is mainly a for form-checking). I only increase the weight if my back doesn't round. Normally what happens... I'll get my back straight for one weight, up it by 5kg for the next week, and I'll be back to the same problem. I don't think I've "fixed" my back rounding, I've just found the weight easier and now my back doesn't round, so it re-emerges when I up the weight.

I've read about so many cues to fix my back-rounding, but it doesn't always work. I feel like I'm pushing my butt and my hips out in this video. Sometimes I'll try with my hips lower, or higher, still the same problem. This was the second set of the day, first rep looks pretty good but the rest are kind of a mess, what advice can people share?

youtu.be/znUf6o7uAvQ

[3SchnitzelsAday]

Ur butt is too low at the beginning of the lift.
Your neck is overextended.
I think you rounded on the last rep because your legs were failing.

[microrahsheen]

It looks pretty good, actually. The rounding doesn't seem that bad to me. Your hips and the bar rise in sync. It appears you are bracing correctly. Do you work your abs/core at all? Are you focusing on stabilizing through your glutes and hamstrings?