My Q5 was in for its 120,000km Cam belt change service. A few days later on the first high way trip while overtaking the car goes into limp mode.

I pulled over and turned it of and on, but would not start. Only cranks for 1 sec and then stops. Got out the laptop and VAG-COM to find this code:

P0299 00 [01100101] - Control Range Not Reached
Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 120012 km
Date: 2025.01.20
Time: 08:51:59

Engine RPM: 2296.50 /min
Normed load value: 99.6 %
Vehicle speed: 68 km/h
Coolant temperature: 91 °C
Intake air temperature: 28 °C
Ambient air pressure: 980 mbar
Voltage terminal 30: 14.340 V
Unlearning counter according OBD: 40
Charge air pressure: specified value: 2550 hPa
Charge air pressure: actual value: 1485 hPa
Air mass: actual value (mg/stroke): 394.0 mg/stroke
EGR Solen.val.: actual value: 99.67 %
Throttle valve adapter: actual value: 99.99 %
Charge air pressure actuator: acknowledgment: 84.29 %
Mean injection quantity: 47.57 mg/stroke

4096 - Bank 1: CMP Sensor (G40) / Engine Speed Sensor (G28)
P0016 00 [01101101] - Incorrect Correlation
Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Priority: 2
Fault Frequency: 1
Mileage: 120012 km
Date: 2025.01.20
Time: 08:52:09

Engine RPM: 887.00 /min
Normed load value: 15.7 %
Vehicle speed: 50 km/h
Coolant temperature: 91 °C
Intake air temperature: 26 °C
Ambient air pressure: 980 mbar
Voltage terminal 30: 12.100 V
Unlearning counter according OBD: 40
Engine start: start synchronization: EPM_MODE_VERIFY
Engine start: start synchronization-Test_Program_Epm st Op Mode State t UBYTE: 33

Cleared code, but car still does not start. Phone the mechanic and had the car toed in.

I was soon phone by the mechanic and told the timing marks still line up.

He then inspected and opted to replaced the belt, the car ran after this, but had very little power and the ECU code as that the Air Mass Filter signal was "implacable" (I don't have the exact code).

He then decided to open the tapped cover to check for damage. The indents on the cam shaft that allow you to access the head bolt did not align with each other. (I saw it with my own eyes, was off by a small amount). There as not visual damage to the rockers (cam followers). The assumtion was that the press fit gear on the cams has rotated. (Its the gears at the back, not the one that is driven by the belt)

He then ordered new cams, confirmed that the new shafts does indeed line up better than the old ones. Replaced both cams and the car runs fine now. No errors, lots of power.

Is it common / possible for the press fit gear to slip?
Is it just a coincidence that this happened less than 50km after the cam belt service?

I want to gather information to ensure that I do not pay for something that is his fault, and if its just coincidence, then I will pay the fair fee.