Wear parts are normal for VW Caddy BSU engine

Hello fellow enthusiasts.
I have two VW Caddys, both manufactured in 2006. They are both 1.9 TDI models with 75 horsepower, and the engine code is BSU.
One of them has 120,000 km on the odometer and has been experiencing problems with the idle speed and while driving. Since it's a long-distance vehicle, covering approximately 140 km per day, I'm not factoring in the driver's skill or driving habits.
Okay, the problem is: the camshaft is worn, the PD elements are defective, and the damage is €2400 (for parts).
Question: Why isn't Volkswagen being accommodating in this regard and refusing to pay for the damages? A camshaft is not considered a wear part.
Sincerely,
Hans

Pictures?

I don't immediately see a connection between worn-out NOx reduction components and defective particulate filter elements, unless unsuitable oil and/or fuel (e.g., heating oil) was used.

Best regards, Rainer.

I will post pictures as soon as I get my vehicle.
"Shell brand oil has always been used, only the very best, specifically suitable for PD (common rail diesel) and oxykat (catalytic converter). Service is performed every 25,000 km (approximately 15,500 miles), including engine oil, fuel/oil filter replacement, air filter replacement, pollen filter replacement, and a complete inspection."

Here are some pictures of the broken camshaft.
However, I'm now experiencing other problems with the car. When I let it idle (without any electrical components running), it runs perfectly. But when I turn on the electrical components, the engine speed fluctuates wildly (600-900 RPM), almost stalling. This also happens while driving, between 1000-2000 RPM. If I stay in that RPM range for too long, the engine starts to sputter. The error memory is clear, and Volkswagen isn't really able to fix the problem.

Which Shell engine oil was used? Was the car serviced at an authorized dealership? How certain are you that it was actually PD oil that was filled?

Shell Helix Synthetic 5W-30. Suitable for Pd catalytic converters, turbochargers, and particulate filters (only the very best).
The car has only been to the authorized service center for repairs. Otherwise, I have replaced the engine oil (with any brand), engine oil filter (MANN), fuel filter, air filter, and pollen filter, and I have performed all other necessary maintenance tasks (such as brake fluid, brakes, etc.) myself (I am training to become a master mechanic for agricultural machinery).
I'm 100% sure because the oil has a VW approval, and it's not exactly cheap (20 liters for 180 euros).