I was having the same problems. Lagging, stuttering, freezing up, screen not registering touches, and the supposedly long lasting battery wouldn't last 2 hours. I searched on YouTube and online, and here is what I heard. LG changed the chipset on the G4, and supposedly this chipset and the version of Android are not playing nice together, causing memory leaks, and all the issues we're having. After doing some research, there isn't a fix for it yet, as fixes are released with updates from LG. There are workaround that solve these issues until the updates arrive. Here are the ones I did to fix mine:
* Search online or YouTube on how to get to developers mode. Once you're in developers mode, go in developer's tab and turn off all transitions and screen effects
* download an app called "battery guru". It's made by Qualcomm, same company which made the chipset in the phone. It will learn for 3 days everything you do, then it will tweak the phone for you. My battery tripled in time, it feels like I got a brand new battery.
* Go under battery usage in settings, it will tell you what apps use the most resources and power. If you're like all others LG G4 users, you'll notice screen and Android system being the two most battery and resource draining apps. Android system there's nothing we can do until LG fix it, but the screen we can help, by making sure the screen timeout is set for 30 seconds, and making sure of you're indoors, you can leave the brightness between 35 and 40
* Download an app to help you check on Android system. I have "clean master", and it tells me what apps are forcing themselves to open in the background and you can either fix the issues or uninstall said app.
* This phone has a great camera, but remember, great camera require a great amount of power to tweak. I go from 100 percent battery down to 60 percent in about 20 minutes by leaving the camera in manual mode and playing around with each options. At the same time, with camera in auomatic mode, I take many more pictures and it drains the battery less than in manual
* Use common sense: great phones provide lots of options for its users, sometimes too many. This phone has Wi-Fi, Bluetooth, NFC, GPS, Android beam, smart share beam, miracast, LG bridge, knock screen sensors, quick circle case sensors, etc. These are all sensors working in background waiting to be used that's eating up your resources. Either turn them off completely if you're not using them, or if you do use them but not often, turn them on only when you're ready to use them. Why would NFC be on if you use it twice a week to pay for coffee with your Google wallet? Doesn't make any sense
* Go into GPS settings and change it to battery saver mode.
* if you follow all of these tips, you will notice your phone's battery lasting for a day and a half with heavy usage, and you'll notice the lagging and freezing up to be ALMOST gone, almost being the key word. Every now and then my phone still lags, but it isn't as bad as it was when I first got.
Hope you are able to solve your issues!
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