Mi3 Internal Speaker Problem

Aug 31, 2015
Hello. I have this problem - internal speaker works fine for few days then suddenly someone calls or I call to someone and the speaker doesn't work. I restart the phone and it works fine. It is a hardware or a software problem?

It wasn't this problem till I try to remove flip cover ( battery cover) to check screen plug because I have a red marks on my screen. But in this time I also made an update to rom 5.8.13. Now I have a 5.8.20 rom and problem is still, but I hadn't this problem with rom 5.8.6 and older roms. And now I don't now that I broke this with hardware or software.