LG G3 screen sometimes doesn't turn on after locked

[Dezso3]

I just did a factory reset of my LG G3 because the microphone wasn't working properly. When I would call someone, they wouldn't be able to hear what I was saying. After resetting it, the problem went away. Earlier today, though, I was trying to unlock the screen after blacking it out, but when I tapped it, it wouldn't turn on. So I pressed the power button, and THEN it turned on. When I blacked it out again (without unlocking the lock screen), and tried tapping it again, it would not light up. When I pressed the power button again, it lit up again. Then, I unlocked the screen, and then locked it and blacked it out immediately. THEN when I merely tapped the screen, it actually lit up, unlike previously, when all it would do is flash the blue light at the top left of the phone. What could be causing this problem?

 

[the Core]

What could be causing this problem?

Hi Dezso3, I don't know the real cause, but I had something similar. My flip cover broke, so I bought a $2 one from Ebay. If I put opened that cover and lay it down on metal (kitchen for example), it would think the cover was closed and the screen wouldn't light up. When I held it in my hand, the screen behaved fine. Is this of any use for you?

 

[Dezso3]

I actually tried holding it in my hand, and then tapping it, but the screen still wouldn't light up. Although, it only did this once the other day, and since I restarted my phone it's behaving fine, so I'm hoping that it won't behave like that again.