[Xperia Z3 Compact Q&A, Help & Troubleshooting] ascendant512:
So I've gone on adventure trying to prepare a new Z3C with working GPS and the adventure seems to have ended in failure.

I can describe some of the journey, and maybe there is advice on what bricked the phone or possibly a way to unbrick it as it is not in as poor condition as the previous one.

The phone arrived new in box with the Sony holographic stickers; I immediately followed the bootloader unlock procedure without any hiccups (to the best of my memory, it arrived with firmware 23.5.A.1.291).

The first failure was getting the phone to boot TWRP. For my previous z3c, this was the TWRP I used.

However, booting it with fastboot boot twrp-3.3.1-0.4-z3c.img

returns the error:

Booting FAILED (remote: 'dtb not found')
fastboot: error: Command failed

The device forums are sparse on this error, what it means, or how to fix it, but I'm used to TWRP being incredibly flaky. I did find that there is a combination of requirements from a kernel somewhere on the device which boots recovery requiring LZMA support, as it is the compression method for newer TWRPs.

The TWRP 3.2 from that post, as well as older TWRPs such as 3.1.1 were usable to boot, and led to the new phone's very brief peak operating state, in which I was able to flash and boot an old CarbonROM 5.1/Android 7 zip. However, TWRP 3.2 predates the phone's renaming from aries to z3c, and that version of TWRP would not flash the latest CarbonROM and Android 10.

From here, things only went downhill. Retrieving images from my Z3C which currently runs current CarbonROM, I overwrite the boot, FOTAKernel and userdata partitions from the old phone using a process like this:

losetup --find --partscan --verbose backup.dd
dd if=/dev/loop0p14 of=backup_boot_14.dd
dd if=backup_boot_14.dd of=/dev/block/mmcblk0p14

Where backup.dd is a copy of mmcblk0 on the working phone and partition 14 is the one labeled "boot" in the GPT (16 is FOTAKernel and userdata is 25). The phone has never successfully booted into anything since, and these are some of the things I've tried to do to fix it:

Using Xperifirm 5.6.1 I downloaded firmware 3.5.A.1.291-R5D for US

Using flashtool 0.9.33.0 I assembled a ftf using the components "fotakernel.sin, kernel.sin and system.sin"

After flashing this group to the phone, it would boot loop the stock firmware (boot animation, freeze, reboot, do "optimizing apps", repeat). The stock firmware would also recognize my encrypted userdata and prompt to decrypt it until I used fastboot to clear the userdata partition.

That's the last time that flashtool worked, though. I later learned that there are preassembled ftfs that can be found, and got the one from this post:

https://xdaforums.com/t/list-ftf-stock-firmwares-concept-18-10-2016.2906706/page-109#post-68187188

Whenever flashing anything to anywhere using flashtool, it spits out these errors:

flashsystem.X10FlashException: ERR_SEVERITY="MINOR";ERR_CODE="0017";ERR_DYNAMIC="80080021";

I haven't found anything anywhere that explains what these mean, or how to solve them.

I've tried checking and unchecking the various boxes in flashtool's flash mode that cause it to skip steps in the flashing process like so:

Flash the D5803_23.5.A.1.291_Customised_Nordic with default settings

When the first step fails out, restart the flash process

Uncheck the box for that step and let it start. It errors out on the next step

Repeat until only system is left that failed.

However, this does not seem to have accomplished anything productive. I also tried

fastboot flash:raw boot backup_boot_14.dd

and

fastboot flash boot boot.img (from CarbonROM's zip)

As well as the above with recovery and FOTAKernel from various TWRPs.

The phone isn't hard bricked, it boots into fastboot mode with vol+ and flash recovery mode with vol-. fastboot boot twrp.img has a few different behaviors depending on the TWRP version:

Nailyk's twrp_z3c_2019-03-13 from

https://www.reddit.com/r/LineageOS/comments/edwnzf
will boot to a black screen. No adb available.

The previously successful TWRP 3.2.3-0 without LZMA compression from NeoArian boots to a SONY logo notably without the Xperia logo on the bottom.

Newer versions of TWRP (3.3+) or lineage-18.1-20210914-recovery-z3c continue to fail with the "dtb not found" error.

It seems almost certain that the path to a working phone will be through flashing it back to stock using flashtool, but I don't see a way to make flashtool work or what is causing the errors.