On the primary side there is a spring between the timed disc and the cam, so any knocking on here will move the cam back and forth. The timing pinions can be tight, don't think I've had one yet that isn't, however I would look to remove any fash'es on the ID of the cam, I've only found one tight one and a quick clean up/polish of the pinion allowed the pinnion to be a firm but not too hard to fit or remove fit. I would also try fitting the cam pinion without the woodruff key and see if it goes on any easier! it could also be that the key isn't a) fitted properly into the cam, or b) sized properly.
Now let’s all have a beer
68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)