There are indeed sources of oil pressure loss on some of the MB engines, but that would be rare. There are pressure relief valves, but they're just a poppet and spring, not much to go wrong. Also, I saw oil pressure loss on an early six that was the head gasket not being properly torqued at the cam sprocket pocket in the front corner. That was after an overhaul and I don't see how it could be a problem in an old engine.

Good luck,