Vacuum line fragility and electronics are possibly problems because of environmental and workplace safety concerns. The switch to soy based oils in plastics are a contributor to the vacuum line fragility. The industry moved towards recyclability of plastic and lower-cost versus petroleum-based plastic. Soy-based plastic eventually decomposes. The wire loom covering, PCV tubing and the vacuum lines eventually succumb to decomposition.

The electronic PCB boards found in various sensors don't use lead-based solder. The current bismuth based solders are comparatively rigid and develop micro-cracks which result in the sensors failing. A good example is the exhaust temperature sensor failures. These problems are found on other VAG cars

The W12 produces an abundance of heat exacerbating the deterioration of the above. Anyhow this is my assessment of WHY.

 

I blame VW and their cost engineering. Hope to replace my vw/conti with a 'real' bentley one day, lol!

 

Let's not even get into window lift regulators. The nylon sliders crumble then the tiny lift wires frey. Say no more! Still like mine, though.