Perhaps not only at high temperature, right?
I think this is the "screen flicker fades darkness" problem described for example here: https://www.youtube.com/watch?v=7j88SysXtw4 and here http://forums.androidcentral.com/lg-g3/527306-why-does-my-lg-g3-screen-flicker-fades-darkness-19.html and here https://www.youtube.com/watch?v=gAUkXLR7eQI , https://www.youtube.com/watch?v=qdg6t_I0Or0
I tried some of the workarounds and worked fine for some days. I haven't tried the 'bake the motherboard' option, because I don't have any way to verify the oven's temperature is in the proper range