WOW lots of maintenance and crew error here. As a licensed aircraft engine and airframe mechanic with many years working on radio engines including the R1900 the ignition issues were the route cause for shutting down number four engine. The condition of the P leads was inexcusable. I would have grounded the aircraft until they were probably repaired. The small points gap on number 3 differently attributed to low power on number three. Also as a flight engineer with over 4000 hours in four engine aircraft, C-130 the pilot broke a cardinal rule of basic a multi engine aviation, you never turn into a dead engine. He had number 4 shut down and number 3 making reduced power, both on the right wing and he still entered a right hand pattern. In my mind and experience not very smart. He didn’t declare an emergency which would have allowed him to request a left hand pattern which would have kept him from turning in to the dead engine.
Lost a friend many years ago flying a twin engine aircraft when he lost an engine on takeoff and turned in to the dead engine when he attempted to return to the runway. The plain rolled over into the dead engine and crashed inverted.

Thanks for posting.