Question Xperia 1 III Softbank A101SO issues Downgrading after a crossflash - Sony Xperia 1 III

Hello everyone.
I bought a japanese Xperia 1 III (Softbank version A101SO) with Android 12 and I've searched for the 13 update but it turns out Softbank didn't release Android 13 on this phone yet.
So I decided to flash the KDDI version to it (with newflasher) and it worked.
But the problem is I got a very weak signal, a battery drain and the 4G rarely appears (always H or H+)
I tried to come back to the old original firmware but the phone won't boot after the flashing process (rollback protection)
The phone has a locked bootloader and it says it can't be unlocked so I wonder if you have a solution for me because I lost all hope right know.
If I can just go back to its original firmware (Android 12 from Softbank) that's all that I need right know.
Thak you for your answers.

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Unless you unlock your bootloader, otherwise, you cannot go back to Android 12 again. If your phone's config name 'Bootloader unlock allow' is No, then you have to stick around with KDDI Android 13 fw.

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FiDra said:
Unless you unlock your bootloader, otherwise, you cannot go back to Android 12 again. If your phone's config name 'Bootloader unlock allow' is No, then you have to stick around with KDDI Android 13 fw.
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Thanks for your reply! I'll have to stick with it then...
But can I flash the Softbank modem to it to have a better signal coverage?

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I think cross flashing is okay but you need to do some search to make sure you flash all needed files to prevent boot loop.

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FiDra said:
I think cross flashing is okay but you need to do some search to make sure you flash all needed files to prevent boot loop.
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crossflashing works but the problem is the Signal and the battery drain.
is there a way to flash other modem files to the phone?

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Try newflasher, you can search the forum for the guide.

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FiDra said:
Try newflasher, you can search the forum for the guide.
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Newflasher is the tool to flash the roms.
I know how to use it since I've crossflashed my Xperia 1 III with another region FW using it.
My question is: is there a way to flash different modem files (and other important files) to the phone with a different region rom to fix the signal and battery drain issues?

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Samuël_Fab said:
Newflasher is the tool to flash the roms.
I know how to use it since I've crossflashed my Xperia 1 III with another region FW using it.
My question is: is there a way to flash different modem files (and other important files) to the phone with a different region rom to fix the signal and battery drain issues?
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Click to collapse
Yes just keep the .Sin files that you fish to flash and remove the rest from the rom folder. And make sure when prompted by Newflasher to "keep user data".

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bentree said:
Yes just keep the .Sin files that you fish to flash and remove the rest from the rom folder. And make sure when prompted by Newflasher to "keep user data".
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ohh! thanks for your tip!
I want to ask you:
do you know the name of the modem files that control the network?

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Samuël_Fab said:
ohh! thanks for your tip!
I want to ask you:
do you know the name of the modem files that control the network?
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Click to collapse
Modem.Sin is the file you are after.

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bentree said:
Modem.Sin is the file you are after.
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Click to collapse
So I've successfully flashed the modem sin file but there's a problem with the camera.
It refuses to launch and the Telephoto lenses are moving all the time (with the noise of the lens moving).
But the signal is back at 4G.

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Samuël_Fab said:
So I've successfully flashed the modem sin file but there's a problem with the camera.
It refuses to launch and the Telephoto lenses are moving all the time (with the noise of the lens moving).
But the signal is back at 4G.
Click to expand...
Click to collapse
no idea with that one... sorry

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bentree said:
no idea with that one... sorry
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Click to collapse
I guess flashing it with other modem sin files don't resolve the issue.
I need to wait for the Softbank Android 13 (if it will be released one day...)

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Thanks to you and people on this post, I've been able to flash fw 61.1.E.5.215 into my A101SO and fix mobile connection and camera by flash .sin file from A101SO android 12 fw. If you still struggle with the camera, let me know. I've seen improvement with battery life and mobile signal, the only let down is netflix wont install from playstore nor playback at full fidelity if I install with apk

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Samuël_Fab said:
I guess flashing it with other modem sin files don't resolve the issue.
I need to wait for the Softbank Android 13 (if it will be released one day...)
Click to expand...
Click to collapse

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Bachtran24 said:
Thanks to you and people on this post, I've been able to flash fw 61.1.E.5.215 into my A101SO and fix mobile connection and camera by flash .sin file from A101SO android 12 fw. If you still struggle with the camera, let me know. I've seen improvement with battery life and mobile signal, the only let down is netflix wont install from playstore nor playback at full fidelity if I install with apk
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what file did you flash for the Camera?

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Ainz_Ooal_Gown said:
what file did you flash for the Camera?
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After I succesfully flashed a bootable fw (XQ-BC72_Customized SEA_61.2.A.0.447 for me), I flash these .sin files from A101SO_SoftBank JP_61.1.E.5.215 right after. The camera problem only rise if you also flash modem_X-FLASH-ALL-4BA8.sin

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Bachtran24 said:
View attachment 5922171
After I succesfully flashed a bootable fw (XQ-BC72_Customized SEA_61.2.A.0.447 for me), I flash these .sin files from A101SO_SoftBank JP_61.1.E.5.215 right after. The camera problem only rise if you also flash modem_X-FLASH-ALL-4BA8.sin
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Click to collapse
Hi @Bachtran24 if i understood you correctly then you have installed a Dual XQ-BC72 to your single SIM A101so version and then flashed the modem files and it worked for you?.
Can you please exactly tell which modem files you flashed? in the ROM folder there are 3 modem files.sin.
When you flashed modem.sin filers which ROM folder did you use BC-72 or A101so.
I have the same issues i have updated to global Dual ROM and now my A101so is not getting any signals. looking for your help

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crazycolor786 said:
Hi @Bachtran24 if i understood you correctly then you have installed a Dual XQ-BC72 to your single SIM A101so version and then flashed the modem files and it worked for you?.
Can you please exactly tell which modem files you flashed? in the ROM folder there are 3 modem files.sin.
When you flashed modem.sin filers which ROM folder did you use BC-72 or A101so.
I have the same issues i have updated to global Dual ROM and now my A101so is not getting any signals. looking for your help
Click to expand...
Click to collapse
Did you see the picture, just flash those 4 from A101SO_SoftBank JP_61.1.E.5.215 folder, delete other. Reply if you cant see the pic, i'll put it in context

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Bachtran24 said:
Did you see the picture, just flash those 4 from A101SO_SoftBank JP_61.1.E.5.215 folder, delete other. Reply if you cant see the pic, i'll put it in context
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thank you for your reply. i can see the picture and got the answer that i should use A101SO folder for secondary flashing. thanks!