check and clean grounds to block, i run jumper from block to cyl. heads. smaller but back-up for block connection. run power from battery instead of at starter to cutdown on start volt drop. might load test battery to make sure it's up to snuff and not getting ready die.

Grounds run to a common point on the starter relay bracket then that bracket is grounded to the head with a 8 ga wire at the same place the battery negative cable grounds to. The batteries are brand new from middle of summer.

I would replace the pickup or swap the dist. more than likely the pickup is reacting slowly. at the speed you are turning it by hand it will have no problem but when in the engine a few miliseconds add up and the pickup will end up skipping to the next trigger point. I have had this happen on efi motors when the crank trigger gets a touch slow. it would run for 5 minutes till it would get out of sync.

Had two of them die in about as many years. Sent them back and they said they were unrepairable. Always carried the cables to allow plugging factory module back in so mine weren't pick-up related. For the cost and poor results it'll be a very long time before I'd ever pony up and try them again.