I only watched the first video. You are allowing the bar to drift forward a little on the way down and this continues on the way up. Right now you are bending your knees first and then leaning over. Try doing both at the same time as you start your descent. Think of keeping the bar over the middle of your foot the whole time. Get tighter. Fight the tendency to relax as you fatigue. I cannot really see your grip. Experiment to find something that is comfortable. Sometimes discomfort will come and go.