Walking left is not bad necessarily. When and why may be.
When I watched your videos and stopped them as quick as I can, where you start your ball seems to be part of the issue.
You start pretty much upright with your ball inside of your right shoulder. From there, your ball comes back so late that you actually need to step left and cock your body to clear your 3rd step.
If you stop your video about a half dozen times, the line from where your ball starts and where your ball is at the top, is inside out.
You then redirect, after a slight loop to deliver inside out. Your position at the bottom on the way back and allowing your swing to get so far away from your body makes it difficult to repeat frame after frame.
My opinion, would be, increase your body angle at setup. Start your ball more to your right and let it pass your right hip on its way back just as your second step clears that area. This would give you a slight outside-in line from start to top. Then all you need to do is let it fall back on the same line and let go. No loop, no redirecting.
Watch your videos and notice the position of your body coming into your release. You have lots of spine tilt but no body angle. Your ball should come back and go forward on a straight line or slightly outside in to inside out. Your head should be over that line or even right of that line. It can only be accomplished with body angle and allowing the ball to swing loosely under your right shoulder.
Here's a Slowinski drill;https://www.youtube.com/watch?v=bq6VZXoXMtg
Here's the entire article;http://bowlingknowledge.info/images/stories/slowinskioct10_swing_slot.pdf