Xiaomi 12S Ultra - after unbrick, lots of troubles


Dec 13, 2020
hello everybody,
i come to you hoping that you can advise me.
Being the owner of a Xiaomi 12S Ultra,i had a big problem trying to flash the "xiaomi.eu_multi_THOR_V14.0.5.0.TLACNXM_v14-13" rom.
my device got bricked, no longer coming out of fastboot mode.
It's by watching tutorials on Youtube that i used Mi flash Tool with rom: "thor_images_V13.0.11.0.SLACNXM_20221010.0000.00_12.0_cn_bbefeb715c.tgz"
(I took this one,because i didn't find _V13.0.1.0.SLACNXM with tgz)
I used MiFlash20210813 because the latest ones (MiFlash20220507 and MiFlash20220218) gave me error: "flash timeout" after 700 sec
The process gave me some errors at the end, but finelly the phone rebooted.
After that,i did a factory hard reset
The problem is that there were plenty of flaws:
Unseen Sim Card.
the battery is discharging faster
WiFi stopped working after a while.
the storage memory fulls up very quiqckly with System data stuffs till the storage place runs out!!!

Finelly, I tried to flash the rom "Xiaomi_12S_Ultra_V13.0.1.0.SLACNXM_20220625.0000.00_China_12_XFT" but it was not better.
The ,Miflash told me again
"error: flash timeout" (but this time,after 1400 sec).
Even if the phone rebooted, ad came as "V13.0.1.0.SLACNXM" the result was not better!
Can you help me please?

Mark F

Aug 15, 2020
As you have fastboot, you can install the fastboot EU version. Look at mifirm.net for 12sultra or Thor and select the latest EU fastboot ROM, no other ROM.
Download to your PC and extracted files. Click on the update ROM file with your phone in fastboot mode and connected to the pc.
You may of course need to use the format data file but worth trying the update first.
Let it finish and reboot after it has flashed.

If you don't have any sims and I had this once, download an A12 fastboot ROM and extract the files, just fastboot flash the modem.img file and reboot. It fixed my phone not seeing the SIM cards.
Once working, then look at booting twrp from fastboot and install. If you are on A13 by then, ignore the no operating system warning and reboot if it says while in twrp only.

As long as you can get to fastboot you will be ok eventually.
If you do downgrade your version, you should format data, so try to get a copy of your data backed up before starting.

I should add that I did have a point where installing twrp just gave me a fastboot loop. I recovered from this by flashing the boot.img file from fastboot. Just to let you have alternatives to try to get around your bootloop.
Last edited:


Dec 13, 2020
Thanks for your reply Mark,
do I have to use Mi flash for this? because, given the previous tests, it may not work...


Dec 13, 2020
Sorry for not having immediately understood the flashing procedures.
I am not an expert on the subject.
But I was finally able to install the rom
Everything seems to be back to normal, the sim card too.
For now I have 11.3 GB of system and 12.4 of system files. It climbs, but more slowly.
I will see tomorrow morning what it is.
I will do the recovery procedure afterwards, depending on the result.
Anyway, thank you for your help.
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