Finally I repaired it. It was really the behavior of this "LOAD INSERTION RESPONSE" or "Quick Response" circuit. I reflowed all components around PWM along with the DIGI+ chip itself and no reaction, no change.
Finally after days of contemplation I looked deeper by the microscope, from an angle and it looked like one or two pins marked on the image below did not have enough tin. I soldered all suspiciously looking joints an all four sides.
Now the VRM is arctic cold and GPU does not go black under load and of course pulses on the chokes are as expected 0, 90, 180 and 270 degrees. So remember to use two channels of the oscilloscope when you have instability problems. You must ensure that PWM gives the proper pulses and they are shifted properly.
Thank you everybody who wanted to help
Posted after 9 minutes 10 seconds:mia писал(а):
Mechanical damage, cracked tracks?
In general it was the closest answer but these pins are so small that I did not expect it
Posted after 1 minute 15 seconds:Roberts3333 писал(а):
ASP1106 = ISL95712
This was extremely helpful because the timing diagram pointed me to the "LOAD INSERTION RESPONSE" circuit.