Just found a quite similar thread by a user that had the same problem, exept that he had 5 pads always illuminated, while on my unit there are 12 pads affected. But the behaviour is the same:
Play+ Lights staying on all the time - Bug / Archive - Polyend Backstage
As I understand that thread I am dealing with a faulty unit, right? How frustrating!
Just purchased it a few days ago at Supersound in Poland…