I was hoping this would have been fixed by now, but it seems to still be a problem. I got my XP a few days ago and I'm having a lot of issues with the WiFi at work.
If I put my XP next to my Z3C on my desk, the Z3C has full signal and the XP struggles to even keep the connection alive. The signal indicator in the status bar hits rock bottom and apps lose connectivity. It also won't connect automatically when I get to work.
I installed all the available updates immediately after booting the phone, so I don't know if the problem was introduced in any of those. I'm on Nougat, build 39.2.A.0.442 now.
Maybe worth noting: When downloading the updates I put the phone in the same place it's having problems now, but it had no problems downloading them.
Has anyone found a fix for this? Factory reset? Send the phone back for service/replacement?
EDIT: Factory reset did not help for me at all. The signal strength seemed fine when I booted into safe mode, but it didn't stay that way after I did another factory reset after that.