I believe M119 engines on 1992 400Es have metal tubes which don't have the problem.
I have opened valve covers on my 92 400E when I was attempting to replace timing chain, my oil tubes are all metal.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.