[Xperia Z3 Q&A, Help & Troubleshooting] chaoscreater:
Hi all, it's been a while but I thought I'd post an update and share what I've found/learned so far....

Basically, I'm still getting the frequent random reboots. I've tried reflashing the ROM and also tested out the latest .232 pre-rooted stock ROM, still getting the same issue. I've noticed that other than Google Play Services, sometimes Gapps will crash as well. But most of the time, there's nothing reported in the system or application crash logs. I've tested with everything running as stock, no additional apps installed. I then decided to flash the Minimal GAPPS 5.1.x and that sort of made the phone a bit more stable, but still reboots randomly every now and then.

Later on, I decided to try a custom ROM that still works on a locked bootloader. I found this here:

http://xdaforums.com/z3/development/d6603-23-1-1-28-t3102271

The chef has provided a .232 firmware for you to flash in recovery, as well as the ROM base for the D6603 model. Mine is a D6653, but luckily the chef has also provided a D6653 patch for you to flash as well. I've flashed the ROM like so:

1. Wipe everything except my external microSD in TWRP. So basically, wipe system, data, cache, dalvik, internal storage etc.

2. Install .232 firmware.

3. Install v10.5

4. Install v12.0

5. Install D6653 v5 patch

It boots up fine but after using it for a while, I still get the random reboots. What's interesting is that I've also tried without flashing the D6653 patch, which essentially means I'm running just the D6603 base ROM on my D6653. It works, but still crashes as well. I just found it quite surprising that a D6653 could run a D6603 ROM, but it does make sense considering the main differences is just the baseband/frequencies.

Anyway, I later on decided to flash the pure 5.1.1 stock ROM, still getting the crash. Again, everything is tested on pure stock, no additional apps etc installed.

I'm starting to think perhaps this is a hardware issue on my phone?? I noticed that sometimes, my screen will show a bit of tearing and then it'll crash not long after. BUT, I also know that as soon as gapps or google play services crash, the phone will crash not long after as well.....

In fact, I later on used Titanium Backup to convert Google Play Services from a System to a User app, the phone will just boot into the lockscreen and then restart every time. This is a bit ridiculous because I've done this several times on other phones before and they never had such an issue. Of course, I'm not saying I always run Google Play Services as a User app, but that was just for testing and I honestly don't think it should cause a bootloop just because of that. I've also cleared dalvik and cache by the way, so it doesn't make sense that the phone boots into the lockscreen and then just restarts randomly.

I haven't tried uninstalling Google Play Services completely, but at this point I'm back to square one as I've exhausted pretty much all my options and it's been a complete waste of time. I'm beginning to hate this phone more and more. The only thing left is to unlock bootloader and play with other custom ROMs. But yeah, flashing the .232 firmware didn't fix it, AND flashing pure stock 5.1.1 Android didn't fix it either...

Just wondering if others have the same issue and any ideas what could be causing it? If I provide some Logcat logs, would someone be kind enough to look into this for me?