Turning this off hasn't worked. I'm going to try again on a different computer on the weekend.
I'll try without using the Sony software, as I think this is causing the problem
Linux went without a glitch for me. Just had to install the android tools with a single command, turn off phone, plug it in while pressing volume up (or was it down for fastboot mode?), checking fastboot devices and proceeding from there with flashtool... if i recall correctly.
For me the lowest volume setting is to loud, and high volume way too high an massively cracking, I guess on the long run it would destroy the speakers.
Is the display brightness range the same on sfos as it is in android? Booted the thing in android for the updates and found it is nicely dark on lowest setting. Unprecedented in sfos device i would say.
I just want to say thank you to all those who helped me