Aftermarket block street strokers.

Yep, common problem with Milodon. They don't pay attention to where they punch the holes so sometimes the washer ends up on a rib. When they make an oil pan for external oiling they should use a different rib pattern. Very simple engineering fix but they have never made the fix in 50 years of production.
Yeah, that is a simple fix. Just making the washer a smaller diameter would fix it.