Re: dillon 650 lube
I probably clean and re-lube every 1000 rounds or so on the 650. Key points: the shaft, a bit of grease on the shellplate ball as well as some on the surface that the shellplate sits on, a slight bit under the primer plate. I have replaced the spring that sits under the ball a couple of times (my 650 probably has 300K rounds through it).
And, I don't have my manual handy so I don't remember what it is called but the wedge shaped ramp that's part of the shell feeder -- I do try to keep this greased a fair amount as I've scored a prior one due to high volume.
I suspect your problem could be solved by tweaking how tight the shellplate bolt is cranked down. I've added the rotary washer tweak to smooth the indexing and it makes the stock adjustment a bit less sensitive (if you do a search on Brian Enos's forum you'll find the tweak). Still, I find that in stock configuration, getting the tension just right is somewhat touchy.