I think I’ve finally found the mystery…
After swapping the nozzle,I found that the 0.2 mm and 0.6 mm nozzles deliver a perfect first layer so I have investigated more on the 0.4 nozzle
Then I found that the 0.4 nozzle uneven worn-out even if I have not printed more than 2-3 kg of filament (the printer is brand new)
I think this happened while the printer was cleaning the nozzle on the bed
I have opened a ticket
The hole still looks fine
The area where the nozzle is cleaned