I don't see how dodgy injector seals would impact diesel getting into the oil, a damaged injector might if it was sticking open but you'd notice this in the way the engine is running and what's coming out of the exhaust surely?
Sounds like a design flaw to methe fuel rail is internal in the head itself
Though it is a possibility, it is highly unlikely that would arise out of the blue without any earlier symptoms. I would be more inclined to to think seals.Thinking it needs a new head is catastrophising a bit, seals and gaskets etc sure I doubt the whole head needs replacing
Sounds like a design flaw to me