Hyundai-Cummins blowby issue

We just acquired a very tidy, 5,900 hour 2007 year Hyundai HL760-7 wheel loader
It is fitted with a Cummins QSB5.9C engine.
The engine starts and runs well, plenty of power and no excess exhaust smoke.
But blowby, never seen anything like it. (venting pipe comes from the side of the block, above crankshaft and exits under the engine)
Puffs pretty hard on idle but actually pumps out a spray of oil when you rev it up.
It looks like the previous owners have tried to remedy it, new rocker cover...

Hyundai-Cummins blowby issue

Hyundai-Cummins blowby issue