Hi Joachim.
I bought the bike with the problem, or to be exact, I didn't have an opportunity to have the bike started.
Since the low oil pressure lamp does not turn off, I am afraid the oil pressure in my engine is less than 0,1 bar !
I don't know if it makes sense that the switch breaks at 0.1 bar. But I suppose the oil pressure is very low when the engine is running at idle. I would guess that the pressure switch should not light up the low oil pressure lamp even if the engine was running at 1000 rev /min.
It sounds very interesting with the oil plugs you mention, I must look into this.
Next step will be to get to the oil pump and see what is going on....
Best regards Erik