Yep, the breech lock cam screw needs to be staked from the inside of the gun to retain it. The cam has two opposing notches in the threded hole on the top for this purpose. Once staked properly from the inside it will not work its way out again. It must be staked from the inside becasue if you have the screw adjusted properly it will be too loose to do any staking to the bottom plate. Similarly you don't want a lock or star washer under the screw between it and the bottom plate becasue it will tighten it back up. You have to stake from the inside....and it doesn't take much, just a little peen with a big flat blade screw driver and hammer all you need. I staked mine about 4 years ago and have never touched it since and have fired tens of thousands of rounds. I do not remove the cam for cleaning.....hell, cleaning, what is that? I just wipe down the insde of the gun with a rag hit the barrel and internals with a hose down of WD40 and then dried. Reassemble and squirt it all with LSA and throw it back in the crate.
Your problem with not returing to full battery could be caused by so many things it is really hard to tell from here. Check the cam first, check the headspace, check the belt holding and belt feed pawls. Might be that last inch or so of stroke that draws the belt that is causeing the bolt to not travel the full distance. By the way, the gun should run dry....if it does not then there is something wrong. Lube just makes it work better but that thing should still run pretty much bone dry so lube alone is probably not the issue. In fact over lubing it may be masking some other issue.