Hmm.. I think that the factory soon realised that it was a major problem that the pump was only a single outlet, as of course the side of the engine that had the most suction got the lion’s share of the oil. They tried to overcome the problem by putting metering jets in the crankcase oil feed connections, and that may have worked well enough with a new engine, but after a few thousand miles and a bit of engine wear, the metering jets would no longer be correct. Pity really, as it is a very reliable pump, despite having a “monkey metal” (Mazak zinc alloy) body. Pumps working in the same way are used to supply oil in small but precise amounts to the bearings of jet engine turbines spinning at very high rpm.