Could I have a cylinder going bad??

[Airn45]

I was in the process of installing an agp wastegate and turned the car on to warm up the bolts for easier removal of the heat shield. I noticed a knocking noise coming from cylinder 3 and see the spark plug cover bouncing. I put my hand on top of the spark plug cover and I can fill the knock. I cannot fill the same knock on the other spark plug covers. Whats going on??

[Airn45]

Found the problem. Spark plug was bent on the end and lost its thread holding it in place.