I did and this time I was able to watch the video. I have never seen anything like this, his leg seems to work just fine until he lifts it to a certain level which causes the "snapping" motion.
His belly might be red/purple from brushing it on the ground/straw/hay when the leg slips, so the...
It is hard to determine whether this could be a congenital malformation or a dislocated hip.
In any case it will get even worse as with increasing weight of the chick the strain on leg and hip will increase as well.