The video didn't play for me. Anyhow, I guess that you comment about air leaks may be the exhaust ?.. or maybe it is actually leaking at the sliding face between cylinder and valve block? - very likely if the machined finish is not perfectly flat or linished smooth? oil liberally to see if that helps? Check with just a little air and soapy water, while turning over slowly by hand. Bubbles will show leaks. Not all passages are primed with air all the time so hand turning the engine can help show what is good and what is leaking.
In the UK we call these "oscilators", as "wobblers" to us implies a sense of imperfect control. Like after a lot of beer, or a child learning to walk. But the oscillating motion is actually well controlled, hence the name.
A very nice looking engine. Hope you figure out the leaks or noises?
K2