Spark plug not wanting to stay put problem

[Supa Ninja]

I wander if someone can help me. I am experiencing a repeated problem with spark plugs removing themselves from the head. They take the threads with them. Now I thought it was the timing so I checked it and it was a lil off, I set it back to spec. Maybe I'm having a vacuum leak and it's causing that cylinder to run too hot. The plug does look a little lean. This is so frusterating. Thanks in advance for the help.

Nick