I too am having problems with the Wi-Fi tethering. I have a Sony Xperia Z2 D6503, bought it on Amazon June 19, 2014. No problem with tethering in the beginning, and no problem with the 4g signal at all. When I link my tablet or computer with the phone, the internet on that device works very slowly. If I try a speed test on the tablet or computer it will generate a network error. I am with T-Mobile I had them check my problem. They found nothing wrong on their end. If I connect to my Wi-Fi at home on my home network cable, I have no problem with either. So I am on lunch at work the other day still having problems with the tethering, a friend on the same network with the same plan I have tethered a signal with his Samsung 5. My tablet had no problem connecting to the Wi-Fi signal it connected with a 38 mbps. Wats up with the tethering issue.
