[Xperia Z4/Z3+ Q&A, Help & Troubleshooting] jurko217:
If you dont want to see all my story, go down 2 see the base of my problem and second question.

Hello, i recently bought this phone in last week, used, for fifty euros and it had 32.3.A.2.33 firmware, and please remember WHITE boot screen.

It havent bootloader unlocked.

For some hours of using, it runs fine, except display, seems to be changed by amateur person, sometimes bad touch sensitivity, but i turned on glove mode and no problem. No lags, camera working, every thing - no problem so far.

And then problem began - after restart for sim change, phone boot animation was very slow, and some display flickering. When it booted, system was very slow, display had very slow reactions, i thinked it was GPU or software problem. After some minutes it itself rebooted, 2 red blinks and then booted very fast.

I tried some restarts, 2 of 5 was this problem.

I tried unlock bootloader, and install TWRP, because i think this isnt GPU problem, if 3 times booted and works flawlessly for HOURS !

Okay, bootloader unlocked, twrp installed, i searching for some roms, but phone have very bad community on XDA, i downloaded 3 roms:

AOSCP 3.5.1 - works flawlessly, no display flickering or something, some bugs like camera with bad quality photos, but after restarts, no display flickering or lag and this is important. But no boot screen (pure black boot screen)

Ressurection Remix 5.8.5 - Android 7.1 - after restart it HAD flickering and lag, something similar like first stock rom, 2 of 5 boots... Not very bad but yes. Very good rom.

LineageOS 14.1 - EVERY BOOT HAD THIS PROBLEM. LAGS, DISPLAY FLICKERING, RESTART AND 2 RED BLINKS.

So i installed again AOSCP 3.5.1 and no problem, only camera.

My not intelligent head was a plan - i prove a downgrade. To 28.0.A.4.8 - stock android 5.0.2. Phone gets black boot screen, and EVERY boot had this problem. Lags, scuttering, flickering... But it booted. I try restart, but no difference. 5 of 5 boots had this problem.

I have installed again nougat rom but not like first, but 32.4.A.1.54. After start flashing with flashtool - report an error with boot_delivery.xml - so i checked exclude bootbundle - no problem with flash. Restarted.

Phone had a BLACK BOOT SCREEN - i looking, because nougat sony roms has a white boot screen.

First boot without Sim card - no lags anytime. It has restarted itself, because i wanted to add sim card.

After reboot, every reboot had this problem.

I tried flash with fastboot twrp like first - https://xdaforums.com/xperia-z4/development/twrp-twrp-3-1-1-z3-z4-t3862684

After fastboot reboot - phone has 2 red blinks and not turning on. I put cable out and i trying to turn on it, but it only vibrates 3 times and nothing. Boot or something, i thinked it is dead, but FOR TODAY im able to get into flash mode and bootloader.

I skip some 5 days with trying with flashtool LP, MM and NOUGAT roms, FLASHING TWRP, Sony companion is unusable, because i unlocked bootloader... My phone (or fifty euros) is in holy phucking s+++ in 2 days of using.

Okay, only twrp what i can boot normally is 2.8.7.0 recovery by old 5.0.2 android Z-ROM https://xdaforums.com/xperia-z4/development/zrom-custom-rom-z3-e6553-28-0-8-251-t3206005

For questions, i tried both this stock firmware and custom rom, rare thing is boot normally, but after restart, no difference.

I tried flash again first stock rom 32.3.A.2.33, no difference, but BLACK BOOT SCREEN aside of white.

One but only one different 3.0.0.0 twrp what im able to flash, only into FOTAKernel or RECOVERY not boot partition, because RED blinks and nothing, but this twrp is from sumire (z5):

https://xdaforums.com/crossdevice-dev/sony/twrp-3-1-0-z5-z5c-z5p-t3571050.

I founded this argument by flashing and aoscp rom and error: This is for (ivy), your device is sumire.

I think i can change update_script - there i changed every ivy to sumire.

Installed with this twrp flawlessly, flashed magisk, reboot.

Again Red blinks...

Now what im able FUNCTIONAL only - flash 2.8.7.0 (too with display flickering and , but this twrp is ONLY for install Z-ROM, other roms like aoscp and RR i cant install because error E1004: cannot install system boot image.

And other twrps i can flash only to boot (kernel) partition, but red blinks or boot again into this 2.8.7.0 recovery.

I am making with Sony, and i had in the hands SO MANY phones , so many from them for repair, from different brands for 7 years, no problem with flashing so far (i thinked i am unstoppable :victory: ), and this is my 2nd phuckedup phone for whole 7 years (first was LG G6) and i wanna help, because i have working flash and bootloader, but i havent an idea what next, because some (80 percent) threads havent functional download links for NO SUPPORT or something, but this is absurd. Like my issue, but this is real. For example: i have Xperia SP for 6 years, with stable recently updated (30.9) LOS 15.1 and Xperia S (recent nAOSP 8.1) for 7 years, flashed anything, anything, anything... Downgraded, upgraded... And no problem for today. Reliable phones as... SP is my primary phone (for 6 years) and S for testing. I wanted something from sony but more performance - functional for 2 days. And karma is here - in xda.

Recently i put it into wall charger, it booted into that 2.8.7.0 recovery and it had 94° and it still breaths ! And really it was very hot ! Normally it had less than 60°.

If i flash through fastboot mentioned newer twrp 3.1.1, 3.0.2, 3.2.3 or other mentioned, what non-functioning there, after that red led blinks, it will go to (green) flash mode.

The main problem is: I am able to go into flashmode and fastboot, i can boot system, but (now) i am able to flash only one old recovery, where i CANT install and boot for example aoscp rom or other rom without problems (black screen, then red blinks, then green flash mode). Original software - lags, display scuttering, graphic artifacts but rare thing is going flawlessly, so i think isnt gpu problem. I need real help. I need this phone and i think it can be recovered. I can send anything from this phone (logs or videos), what would be helpful.

After factory reset + system format, in that old recovery, i have in internal storage (sdcard) folder with name 0. Everything cleaned, but this folder remains.

So there is second question, someone experienced with this issue ?