[G4 Q&A, Help & Troubleshooting] yankeetr:
Some ideas

YES. I joined just to post this reply lol. I have an unlocked H815 (Bought from Amazon, included documentation was in Czech, Slovak, and English) and I've been having this issue for weeks now. I couldn't find much on google and thought it was just my device, but now it seems more and more people are having the same problem. It is incredibly frustrating and it hurts.

Symptoms:

- Randomly (6-7 out of 10 times I want to use the phone for whatever) it'll throw itself into a reboot frenzy til it decides to stop doing it whenever, usually after 5-15 reboots or about 5-15 minutes.

- During the reboots, sometimes it'll reboot even before the phone boots up at all (on the LG boot animation).

- And for the times it does boot up, it'll reboot again within up to 20 seconds or so.

- Some reboots are immediate - phone shuts off and turns on again immediately randomly. But for some reboots, the phone freezes briefly before the reboot. On some of these freezes, there's a horizontal screen glitch at different heights every time.

- During the reboots the phone overheats considerably.

- The battery drains very quickly during the reboots. Percentage "skips" occur frequently.

- It also sometimes "optimizes" apps...

- The number of apps it needs to optimize for whatever reason can be different (I pulled the battery out several times when it was "optimizing", and the number would vary; though it did not boot at all until it finished "optimizing" apps, which took forever).

- Not sure if related, but just 3 days ago completely out of the blue overnight (no updates or anything) the camera developed a green blotch on the upper right-ish side too; seems to go away or get stronger depending on lighting. On google I found a Taiwanese H815 having an identical problem too so it can't be a hardware problem; also due to the fact that it almost immediately disappears when a different camera app is launched under the same conditions (such as Snapchat).

Device:

- Unlocked H815 European model.

- Kernel version 3.10.49

- Build number: LMY47D

- Software version: V10d-EUR-XX

- No root. No unlocked BL. All stock except the launcher (Nova). Plenty of storage space.

- Network is T-Mobile and have a 32GB MicroSD inserted.

What I've tried so far:

- Tried using the phone without SIM card. Did not help.

- Tried using the phone without MicroSD inserted. Did not help.

- Factory reset and immediate restore from LG backup. Did not help.

- Factory reset and no restore - only contacts. Seemed to work fine for almost a day, then problem came back. Probably a coincidence it ran okay for a bit.

- Since the phone overheated and the battery drained very quickly during the reboot spells, it stood to reason that the CPU was being stressed considerably. Most likely by some app or process obviously.

- Tried disabling some "stock" apps after a clean factory reset (the stock apps were the only apps on the device). Tried Google Play Services, and most other Google apps. Tried a few LG apps too. None worked.

- Tried updating some "stock" apps after a clean factory reset; same apps as above. None worked.

- From developer menu, enabled "Show CPU usage". The goal was to see what processes are running during the problem to see if it's associated with a memory leak or a CPU stress. No process seemed to stand out. No memory or CPU leaks as far as I could tell.

- Enabled event, kernel, main, memory, power, radio, and system log from hidden menu (277634#*# -> SVC Menu -> Log Service -> Log Enable). After a random reboot, copied log files to sd card from the same menu in hidden menu and tried to analyze them to see if there was a smoking gun. Logs are huge and I merely looked at the end of them, but to no avail so far. Interestingly though it seems the kernel log was cut mid-line on the last entry...

- I also noticed that after a factory reset, if you opt not to restore from a backup, the phone requires an internet connection to be set up. After the phone is ready for use, the Software version is listed as V10d-EUR-XX. The phone did not ship with this version. I believe it was V10a. For whatever reason, even after a clean factory reset, the phone runs the seemingly latest Software version. Not sure if this information is of any use, but it may be relevant.

I love this phone and when I got it, it was working absolutely flawless. Now with the software updates it seems it's just gotten buggier by the day to the point which it's pretty much unusable now, very disappointed. Hopefully this info will be useful to some of you out there.