Seems pretty clear now.
My mate took my in a Group C around Hockenheim (short circuit) and even though the wet sump was extensively modified he had to back off like Tom due to "0"
oil pressure. And it took "ages" to recover.
We have yet to see a wet sump able to cope with those g-forces... Surely your son was too preoccupied to race rather than watching the
oil pressure gage. (you can't blame him for that)