Over tightening the flange nuts can easily distort the carb body. To check it and clean and clear it properly you will need to take off the large union nut on the bottom and remove the jet block. This is best done by heating the carb with a blow lamp or air gun and tap it out with a round wooden dowel as near to the size of the jet block as poss. I often use a hammer handle. Sometimes you can polish the body or slide to get free travel and I've sometimes had to resort to a fine flap wheel, or simply a heavier spring, but that make it harder on your wrist.
Before you reassemble blow out all the drilling with particular attention to the one that lines up with the tiny hole in the bore as viewed from the flange end. These tiny drilling get blocked up with white verdigris and are best poked through with fine wire. Also a good opportunity to check the flange is flat by rubbing it on some emery paper taped to a surface plate or plate glass. Ron
PS just looking at your video, the slide doesn't seem to stick that badly and the spring should overcome it. My guess is that you over tightened the nuts which should have spring washers and only done up to 6 pounds torque. If you've permantly distorted the body? You will have to resort to the flap wheel as you can't buy a new body.
email (option): ronpier@talk21.com