[Xperia Z Q&A, Help & Troubleshooting] Hubriss:
I recently bought a Sony Xperia Z C6603(used).It came with JB 4.1.2 on 10.3.A.0.423 firmware.It had an unlockable bootloader(but not unlocked).I did the following to it:

1.Rooted with DooMLoRD's method

http://xdaforums.com/showthread.php?t=2186368

2.NFC stopped working after root, so applied this technique

http://www.youtube.com/watch?v=ts8rbhZpQOQ

3.Soon after, an update came up on Sony PC companion for JB 4.2 with firmware 10.3.A.0.423 so I got my device updated to the new firmware.

[But after this update,I lost my root previleges.So I had to root it again.]

4.Rooted again with DooMLoRD Easy Rooting Toolkit (v17) {perf_event exploit}

5.Installed CWM Recovery using this method

[After this root, however,I lost the Bravia Engine functionality in Album(it still worked with videos though)]

6.Made a TA partition backup using Backup-TA v9.6

After all this,the phone worked like a charm.I had rooted a locked BL & installed a working CWM Recovery.It was all I needed.

Then something strange happened.One day,I tried to turn on the Wi-fi and suddenly the phone rebooted and the SONY logo popped up.

I thought it was strange but then I thought it could have happened due to some software error or an app malfunction.

After the phone had booted I saw something weird on my Lockscreen.The Lockscreen clock was missing & in its place it read

"Loading..."

Then I pressed the Home Key & all i got was a black background.But I could still see the notification bar with time,network & battery status.

But the screen wasn't responding anymore.After a few minutes like that,it rebooted again.And so it kept on and on.Until I finally decided to Hard Reset[Power + Vol up]

At this point there was a new firmware upgrade on PC Companion(not OTA) & I had been thinking of updating my device, when all of this happened unexpectedly.

Nonetheless I decided to see if the PC companion still recognized my phone and if it did,I would try and flash the new upgrade.And it did & I flashed the new firmware 10.3.1.A.0.244.

The upgrade was successful(as in,there were no errors during the whole process).I powered up the device & was hoping to see a fully working phone.

But to my dismay, I was greeted with the same Lockscreen with Clock missing & "Loading...." written in its place.

I was utterly heartbroken & kept contemplating what might have gone wrong.I read up a lot of articles on XDA regarding Xperia Z devices & could't find anything that I could relate to.

The ones that seemed similar where left unanswered.

So finally I decided to downgrade back to its original firmware & see what I could do from there.

I tried searching for a C6603 10.3.A.0.423 firmware from my region but couldn't find one.Then I found the same firmware for C6602 for my region & flashed it on my device using Flashtool.

After the flash,however,I saw something strange.On the screen after the first boot,I saw something like this

POWER OFF

Please wait for Power Off Button.

USE PHONE​

I selected the USE PHONE option & I was taken to the Homescreen where everything seemed normal.

However,the network was missing & the wifi did not respond.

Thinking it had to do with the C6602 firmware,I decided to flash a C6603 10.3.A.0.423 firmware from another region.

[Please note that while using Flashtool,I have always performed a clean wipe]

Doing so didn't help me either.The mobile network was still missing n wifi still unresponsive.

After this I tried EMMA but without much luck.

Right now I have a phone which boots up to the Homescreen & then restarts after a few minutes.

I cannot however access the app drawer or the Settings Menu anymore.

And most icons are unresponsive except Bluetooth,GPS & Display Brightness.

I have even restored the backup of the TA partition(which I had taken before it started malfunctioning) but to no avail.

If there is anyone amongst you who can help me restore it back to normal ,I would thank you from the bottom of my heart.

Regards,

An Xperia Z owner in despair.

Edit:Changed Title from "Xperia Z:Close to Bricked" to "Xperia Z:Bricked after turning Wi-Fi On".