I sort of got the same problem after the second time I did a factory reset.
I did the factory reset and as soon as it turned on, I used my google account to sync everything. Funny thing is I did that twice and got the brightness problem twice, also some icons disappeared from the Notification Bar when swiping down. AND I did factory reset 2 other times, skipped everything, went sync on settings and I didn’t get these bugs on these tried. Pretty weird.
Hey there. I flashed the ROM from the update section of the alldocube website for M8 and got the same problem. My version was M8 V1.1 20190122 and the one on the website is M8 V1.0 20181201 (and it was saying it was actually from 2019 05 20, but they didn’t update the download link).
ANYWAY, to fix it I used the factory reset. Settings > System > Reset > Factory data reset
It worked flawlessly.
If you still have this problem, try searching maybe for a version dated like 20190122 or something and flash the ROM.
My tablet is have the v1.1 20190122 ROM. I solve the problem, but I couldn’t type the solution in the topic. I download the Brightness app from the Play Store, and in the app I uncheck the Auto brightness checkbox, then works fine the screen brightness controll.
But the B20 frequency is still not working.
Is there a solution to this?