Time zone resetting itself after Marshallow Upgrade

[scooterpooch]

My Sony Xperia Z5c upgraded to Marshmallow on the 26th September on the Telstra Network (Australia) - yay! Good to get the update, but the time on my phone has been resetting itself to odd times since the update.

One day it was 12:34pm and the time was saying 3:34am. Often it is 2 hours out, eg today it was 1:00pm and the time displayed on the phone was 3:00pm. 

I've found that if I disable automatic network provided date/time and time zone, then re-enable it again, it is reset to correct time. But obviously I don't want to keep doing that, especially as I rely on my phone as my alarm clock.

A common theme has been going into Gmail to check mail, and noticing the time has been different once I exit Gmail. 

Is anyone else having this problem and found a permanent solution? I've googled this problem and come up with nada, is it just me?

[Uliwooly]

Could you test it in >>> safe mode

[scooterpooch]

Hi, thanks for  your reply, appreciate the help. I neglected to mention this problem only happens intermittently so I'm not sure turning safe mode on would help track down the cause. I did try it for a little while but I wasn't sure what I was looking for, and then I didn't have use of the bulk of my smart phone features, so not something I could tolerate for long!

Someone else on another forum suggested a factory reset, which I might try, which is a bit drastic, but I'll attempt it as I'm also having other problems after the OTA Marshmallow update, eg Bluetooth audio connection problems. Cheers.