VTG Fault: P00AF, P2563, P0299 - Troubleshooting

Good evening, everyone.

ich habe ein Problem mit dem Polo meiner Mutter. About the vehicle:
VW Polo 6R
Year: 2010
1.2 TDI
MKB CFWA
Mileage: 180,000 km.

During the second-to-last week, the MIL (Malfunction Indicator Lamp) and the glow plug system repeatedly activated, and the vehicle lost power.
According to VCDS, the following errors were stored (File 1, attached).
-Wastegate valve for turbocharger 1 P00AF - stuck.
- Position sensor for boost pressure regulator P2563 - implausible signal.

After a visit to the workshop, it was stated that the VTG adjustment mechanism is stuck or carbonized and that the turbocharger needs to be replaced. However, I find it hard to believe this, as the problem didn't always occur and I couldn't reproduce it. I drove the car on an extended test drive on the highway for 100 km. I tested it under various load conditions, including sudden acceleration and reaching the maximum speed. No errors occurred. The next day, the errors reappeared in city traffic. I manually actuated the pressure sensor of the turbocharger with a pump, and the rod moved visibly (how far should it move?). The sensor also maintained the vacuum. Then, I tested the vacuum system with the pump. I disconnected a small hose from the vacuum pump and applied vacuum. The vacuum was maintained here as well, although only minimally (see picture), but it was maintained.
After that, I replaced the pressure sensor (N75). After installing an original part and clearing the error memory, the following error appeared on the first test drive:
Boost pressure control, P0299 - Limit exceeded (too low).

I can trigger this error by flooring the accelerator in third gear. Around 80-90 km/h, the car throws the error, the glow plug indicator flashes, and the engine goes into limp mode. After clearing the error, the car runs normally again up to 90 km/h. However, during the test drive, I also had the P00AF error code stored in the diagnostic memory.

Could it really be that the VTG strut is stuck or jammed? Why was the car able to reach its top speed before the N75 was replaced, and why did the errors (P00AF and P2563) only appear sporadically?
I don't hear any significant loss of boost pressure due to a leak.

What would you check next, or can someone help me? What can I potentially log using VCDS?

Thank you very much, and have a pleasant evening.

Please observe the forum rules. It's obvious that you don't have a Diesel mechanic VCDS version.

[Translating...]

https://shop.dieselschrauber.org/en/obd-support-key-p-112.php