Please excuse the late reply.
The debug info looks normal. Both players have their own IP and MAC address. So I think this is not the cause of the problem. Do both run the same Max2Play version? Which Pi are you using with the two players?
Please test the faulty sound cards on other Pis (and their working Max2Play images) to exclude a hardware defect. Please also test playing local audio files. Do the dropouts really only appear when you play music from your network storage? Are the two affected players connected to the network exactly the same as the working ones? Please delete the network entries in your router again and reconnect the players with a fresh image.