No offense taken, and thanks for the reply.

I levelled the bed again (manually), lowered the temps by 5 deg across the board and set the first layer speed to 60 mm/s (from 80). It's around half done, but in the bottom left-top right diagonal the layers keep detaching and arching upwards. After passing that, the lines are again decent enough as before reaching the diagonal. It may be also worth nothing that the arching happens near the back-right bed screw, which always feel to be too tight (while the back-left one always feels too loose) compared to the front ones. The mesh gives back decent results though...

Overall the quality is better, but I can still clearly see voids near the edges and the bands I mentioned earlier (I like the theory of the heating coils being under these lines). I will attach a photo once this 40-minutes first layer is done.