So there seems to be a pattern with the freezing/lockups: they always seem to involve a transition or animation, such as opening/closing the keyboard, hitting one of the nav buttons, windows popping up, etc. The problem is that it isn't consistent and just happens randomly when a transition or animation is occurring.
Someone in another thread was able to get a kmesg when it was happening and said that the HW composer freezing may be the reason for this. So what I suggested was disabling HW overlays in Developer Options (see screenshot). So far so good, but that's an n=1 sample size over roughly 13 hours, so anyone else who is having this issue, it would be great if you could try toggling this setting to see if it helps.
The only issue I've encountered doing this is random choppy scrolling and animations, but it's no way near as bad as the usual slowdowns and turning the screen on and off clears it up. My theory is that these slight slowdowns would be freezes of the HW overlays was on.
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Sent from my LG G2