there are different combos of pans and gaskets---why are you using a one piece gasket?? they have different combos of thickness for the front/rear part and you may have wrong combo--changing the pan to a chinese or el cheapo nockoff will not help--

and is your engine one or two piece rear seal and what front cover??
Rear leaks can also be from between the rear cap and block where pan gasket fit has no bearing