Cyanogenmod LG G3 crashes and does not boot I have recently rooted my LG G3 D855 and installed the latest stable Cyanogenmod release (Android 5.1.1 Cyanogenmod 12.1-20151117-SNAPSHOT-YOG7DAO1K8-d855).

Every few days it happens that the system crashes. So far it has only happened when I was not using my device (e.g. phone in my pocket). When I press the power button to turn on the screen nothing happens, even after several attempts and waiting between attempts. I believe that the phone is actually off during this phase as no phone calls go through.

Trying to press the power button for longer, hoping that the device will boot, proves to be unsuccessful as well. Trying the recovery buttons combination is inconclusive as well. When these issues occurred the battery was always almost full.

Luckily enough on this phone it's possible to remove the battery, and this is only thing that works. Once it boots up everything seems to be working fine. But obviously this is a really annoying issue and it's making my phone be unreliable.

Everything was working fine prior to installing the custom cyanogenmod ROM.

Is there anyway to find out what's causing the issue? And of course, are there any fixes for this?
I would recommend a hard reset in recovery. If you cannot boot into recovery, try using a computer to re-flash the system.