Oil pooling

It's an old SE trick to use a thin film of grease so the gaskets release and can be reused. I've done it before too - with cork gaskets. It used to be that way for holley gaskets too before the reusable ones were cheap.
My impression is the rubber gasket is moving around. I would replace the rubber with cork, make sure the cover flanges are not tweaked and oil/grease free, and use 3M weatherstrip adhesive to attach them to the covers. If you want to at that point, wipe your fingerover the head gasket flange with a little grease to leave a film. Not enough to see a layer of grease - only enough to make it slick. If you don;t want to just make sure there is NO grease or oil on the flange where the gasket will hit the head. Then put the covers back on, tighten the lower 3 bolts, center out, then the top two, and don't overtighten. I had the same set of cork gaskets on a 440 for 12 years at one point ad that was being re-lashed 3-4 times a summer. They's still on the engine but it's with a new owner. No leaks. If you don't use grease the cork will bond to the head and will tear bits off when you go to loosen it after some heat cycles.