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
Lumia 1520, Surface RT