Refitting Cam Cover

[topcat1]

Morning all, my cam cover is back from the powder coaters, have bonded the RG gasket on to the cover and upon refitting the cover- it appeared to keep rocking as if there was something in the middle (rocked length and width ways). Removing and checking everything twice (all appeared fine) I have fitted all bolts and very slowly gone up and down slowly tightening them, eventually all appears ok and the 6 nuts in the middle are also tight.

I'm happy with it now and going to run it up later minus the bonnet to check it has sealed well, but I'm still confused as to why it did not just pop straight on happily, all I can think is that the 6 inserts for the spark plug holes were tight going back into the plug holes. I continuously tapped this area down with a wooden punch and hammer as I was tightening the fixings and all sounded and appeared good at the end.

Any thoughts on this or most likely that it was just the plug inserts that were tight?