(In reply to Sérgio M. Basto from comment #10)
> I send in attach full dmesg.txt and Xorg.0.log

Thank you for the logs.

I tried 4.15.12 on a G98 (9300 GS) but could not reproduce that issue (I had
two screens: one connected over VGA and the other over HDMI). 4.15.12 should
not have any new patches over 4.16-rc6, so you don’t need to try 4.15.12.
I’ll see if I can find some errors in the patches that went in 4.15. If you are
able to bisect the faulty commit that went in 4.15, that would be really
helpful.