With just about all product lines, the most expensive products seem to have the poorest record for overall reliabilty, thanks to pioneering technology.
Go back a decade. The W140 was the least reliable of the MB products.
BMW's V-12 cars (especially the 1988'ish versions) were troublesome cars, to the point of depressing resale values to levels below "garden variety" 5-series cars.
Is this right? Nope. They need to get their act together.
1998 C230 "Black Betty"