The issue realistically can only be down to:
Cylinder bores out of spec
Piston rings incorrect gaps/faulty
Worn valve guides
I’ve listed them in what I would suspect as the most likely to the less likely. If it’s all 3, then you got sold a proper lemon.
Have a look in the breather pipe that attaches to the inlet manifold. You’re looking for oil in that pipe.
Now this is an unlikely potential fault, but the 197/200 has a valve on that pipe. I’m can’t say 100% that the valve is a one way valve, but it’ll almost certainly have a diaphragm in it. If that was knackered, it could be allowing oil to pass through all the time.
But I’m only basing this theory on my experience of bmw cam covers that have a breather in them. If they’re knackered, they drink oil, so you never know, it could be a simple fix.
I’ve got one of those valves in the garage so I’ll have a look when I’m home.