So, my LG UHD 770T died and I replaced that with Sony X75H, its been two days since the TV was delivered and these two days are of extreme frustration.
First thing on day one there was issue with casting screen, had to reset the device. On day two all but preinstalled apps were working. Rest everything ie Hotstar, ZEE5, Sony Liv etc just didn't work, reset it again.
Now, on third day some apps are working extremely slow and some dosent work at all. Feels like I had just flushed 60k down the drain. It's been nothing but frustration from past 2 days and Sony support people are not helpful in India.
FYI: WiFi network speed on testing in TV is showing 125 Mbps. So, not an network issue.
I know you have already reset the TV; however, just make sure you perform Forced Factory Reset as described in this article .
Feel free to x-post in /r/Bravia to see if anyone has the exact TV. However, from my experience with Bravias, this is definitely not normal behavior and is most probably indicative of hardware failure.