Mine worked perfectly during the first 4 months. Then suddenly it wouldn't anymore connect to wifi routers. That is, low signal, does not reconnect, no signal at more than a few meters away from router, etc.
I eventually sent it for repair with clear explanations, but all these ah did was to re-install the software... I got desperate until a few minutes ago when I tried to open and clean the contacts of the back cover. It didn't help, but I tried instinctly to test the wifi signal after applying pressure with my thumbs against the phone's screen, so as to improve the contact with the back cover. Result = instant improvement from 2 bars (2 meters away from router) to 5 bars!
Next step, I opened the back, and with the help of a knife, I bent slightly the metal parts that are used for antenna contacts with the phone. I put the back over and miracle, the signal is now perfect with 5 bars, and without having to press the phone!
Well, I don't know until when the trick will work, and if you attempt to do it, be very careful not to spoil these metal parts. I'm happy for the time being