Hi,
I got a new Xperia XZ. Soon after setting it up, I noticed that the brightness keeps alternating up and down in a 5 seconds rhythm. Adaptive brightness is switched off though. It's always three small, distinct dim steps up and down, very regularly (too regular for a battery fault?). When it occurs, the brightness slider position doesn't change. It happens while typing, too, so it's not a beginning inactivity switchoff.
As advised by Xperia support, I deleted cache, started the phone in safe mode, problem remained. No Sim or SD card was inserted to the phone yet.
Then I resetted it to factory settings, and tested for a while on pure settings (with no connected accounts and imported settings, but with connected WiFi), and the fluctuations didn't show!
However, when I resetted once more and connected the phone to Google account again and restored settings from my current Xperia Z3 via NFC, the fluctuations were back instantaneously.
I got no idea what might cause this. Which settings or apps can cause this effect at all? Any ideas? How should I proceed?
