I meant to update this thread before but it somehow slipped my mind. Short version was user error was to blame, the long version is below.
I called Dillon's customer service and after explaining my problem the guy said you haven't switched out the LP priming tube for the SP priming tube. I assured him I did switch them out but he insisted it's the only reason primers would be going in sideways....
So I checked the machine while he was on hold and turns out he was 100% correct and I've no idea why I was convinced I had switched them out
Well after profoundly apologizing he said to give him a call if anything else crops up. Nothing did and the machine was running 100% as it always has done.
He also assured me the wear marks were perfectly normal.
After an hour and some 500-600 rounds later the pawl return spring broke. This spring is worked every pull of the handle and after two years of service and 10,000s of rounds later it was inevitable.
I dropped Dillon an e-mail asking for a replacement (plus a spare for the future) and within a few hours received an e-mail to confirm that the springs had been mailed
I got them in the post one week later (shorter than expected as I'm in Europe and Sinclair take two weeks) and I was back in business.
This is the first time I've had any problems with my 650 and Dillon's staff know their stuff and their customer service people are just incredible, extremely courteous/professional even when the owner is adamant he switched out the primer tube
Nothing in life is free and I know that this lifetime service of the press/free replacement of broken parts is built into the initial price of their equipment.
I bought this press with the long term view in mind and it's comforting to know that Dillon is always there should any hiccups arise, if it's 10 months from now or ten years from now.
I also solved my priming problem by buying another 650 so caliber changes are well under 5 minutes now