Manfrotto 804RC2 head wobble
I've made a new video as I wasn't sure what was tight and what wasn't:
As you can see the wobble is rather heavy. We'll see what their service dept. says.
Your too high up, we need to see what the tripod is doing, instead were just seeing a moving camera.
In the first video, it looks like you just need to push the locking clip in with your thumb. It may be spring loaded, but with the extra weight it may need a little encouragement. Ive got a 327RC2 and after a trip to humid hongkong, the springs just didn't seem as good at they used to. I stripped it down and found the aluminium to have a slight powdering coating, I cleaned it of, a faint drop of oil on the shafts, rebuilt it and now its a finger snapper