It has valves box, no independent N75. Maybe the cause of failure was compressor surge when he released the accelerator pedal in 1st. The boost at that moment was 2570mbar and the blades got bent. The shaft and turbine wheel are ok, only the compressor wheel was damaged.

I've got 2570mbar values also with stock map, low load. I've been logging the car with a mechanic and it just spikes even with half throttle.

Changing the subject, I've seen a similar case on an Octavia 2 VRS 2.0 CEGA, hybrid turbo set on 2680 mbar absolute pressure. This guy has a 2bar relative boost gauge and it spikes to around 3200 mbars. The actuator has a position sensor and no errors are recorded. I know that boost spikes at low rpms are normal, but not 500mbars difference.

Then you could change valves box (sometimes fix it) or do the well known independent n75 mod.

maybe misaligned actuator arm

Thank you for your suggestions, I wrote a new flash with stock boost 2050mbar and raised only IQ 56mg/cyc. I will give further updates after my friend will change the vacuum box.