Dario – a couple of thoughts.
1) If you have trouble following an upgrade, re-initialize the unit as described in the UM.
2) These products are guitar pedals, and can easily be overdriven if connected to a DAW or suchlike. It is your responsibility if using it as anything other than a guitar pedal to make sure that the levels are correct.
3) It sounds like you have a complex setup that may well have its own problems. I myself suspect that there is nothing wrong with the pedals, and that the problem may well be how they are being used. If this is the case there is no point spending your time and money returning them.
4) If you believe that the pedals are indeed faulty, it would be good if you can set them up in a simple way to prove this. Example: guitar – pedal – amp. My concern is that you will go to all the trouble to send them to us and we will find nothing wrong.