I have update, my MC7000 returned to normal by itself. The only change was to start using it in a stabilized electrical network. I was using my MC7000 in a pub where the electrical network was not stabilized and there was no quality. With the pandemic I had to stay at home where it is connected to a stabilizer and an electrical energy filter (it may have another name in your country). For me it worked and so far it is working perfectly.