Sony has issued an over the air update to the Xperia XZ Premium, which brings the September 1 security patch, improvements to Wi-Fi performance as well as the run of the mill bug fixes and optimizations.
The firmware carries the build number 45.0.A.7.137 and should roll out gradually among Xperia XZ Premiums. Its footprint is rather modest at 115.7MB so chances are it doesn't include any hidden features not mentioned in the change log.
Leave us a tip if you received the update, mentioning the market where you got your phone.
yep, go to wifi options, turn wifi always on. Solved.