[Giovanny]

Seems like you have a software problem. Try installing the original stock ROM and reinstall a custom ROM. Once you reinstall Mighty do another hard reset and that might fix it. If it doesn't than I guess you're on the loose becasue if you take it to the store that is the first thing they will do which is a hard reset. Like you said it will work for a few days but again it will persist with the problems. I guess there is no way for you to proof that the phone is bad.