CM12.1 Latest Nightly brightness and heating problem. Please help

Hi guys, I was using CM 12.1 lollipop 5.1.1 nightly on my LG G3 on October. It was working fine then, everything was flawless. Until, yesterday I decided to try out the newest update. It started to dim the brightness by itself whenever the phone heats up. I had this problem when I was using stock rom but solved it by entering the hidden menu and disabling any heat limiting and performance limiting features (3845#*852# method). But when I tried this method again, it says USSD code and nothing happens. Also I tried kernel editing app from the appstore and disabling any core limiting feature and thermal features did not help at all

Please help me this is irritating me so much especially when I play mobile games or browse web for couple of minutes