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S21 5G stuck in reboot loop after One UI 5.1 update

(Topic created on: 29-03-2023 01:13 PM)

I have an issue with my corporate phone (S21 5G) that might be same as other people here on forum.

New update was pushed 24th of February containing new One UI version release and after that phone is just stuck in the infinite reboot loop. Top part of the phone gets very hot and phone restarts just after couple of seconds.

I'm unable to roll back the update.

I can't backup phone to PC or migrate my data to a new phone as phone keeps crashing.

I have tried clearing cache but this didn't help.

I have tried Repair Apps option from recovery menu but it didn't help nor seems to do anything.

I have tried safe mode but phone reboots even when running in safe mode.

It's OK to enter pin code for SIM but as soon one enters pin for the phone itself and it starts working it just reboots after couple of seconds.

I was in a situation when I was able to get my phone working for a longer period of time (i think it was half a day as longest) but then same issue happens. I was unable to figure out what causing this but it feels very random.

I have no idea what is wrong as phone doesn't report any issues nor there are any logs that I can check to see why exactly reboot was done. Considering "Phone Restarted" notification I assume that this was a controlled restart and not just a crash.

I don't want to wipe it but it seems like the only possible solution. I'm extremely disappointed in how Samsung is handling this. I don't know how many people are affected but there are some of us who do. Currently i have to use my 10 y.o. button phone in hope that Samsung will fix the issue and push a new update or revert existing one so that I can keep my data and settings and don't need to reset my phone. At the same time there is no guarantee either that even after reset phone will get the same SW update and start rebooting.

Product name: Galaxy S21 5G

Phone model: SM-991B/DS

Serial number: R5CR71VZP1M

Current version: G991BXXU6EWAF/ G991BOXM6EWB4 / G991BXXU6EWAF (yes, same number twice)

Security patch level: February 1, 2023

One UI version: 5.1

Android version: 13

Kernel version: 5.4.147-25884040-abG991BXXU6EWAF #2 Mon Jan 30 19:22:03 KST 2023

Build number: TP1A.220624.014.G991BXXU6EWAF


Hi. Samsung says: "backup data before upgrade".

OK, you'd try almost everything possible.

Try starting the phone without SIM. If is doesn't help, you can try flashing the last firmware using Odin if you know how to do that. It is possible that flashing the upgrade was incorrect and this can fix it. If you use HOME_CSC file, the data won't be deleted.

Please never consider that data stored only iin one device are safe, a daily backup is must have.

Samsung S24 Ultra Black 1 TB | Pixel 8a Bay 128 GB | Samsung Galaxy Tab S9 256GB
Samsung Galaxy Watch Ultra | Samsung Galaxy Buds / Buds2 / Buds2 Pro


Thank you for your tips.

Unfortunate I have Enterprise Android installed on my phone that limits what can be done. So I'm unable to flash any firmware on my phone (I would ideally like to have non-enterprise Android version on my phone).

Backup of data won't help when you can't restore it due to phone rebooting all the time. I actually managed to create a backup during last period when phone was working for longer than 1 min. So I have it now at least.

Considering this is corporate phone this issue heavily impacts my day to day work as I can't attend meetings using the phone, I can't be reached by customers nor can I use 2FA solutions for work and banking as they all require a phone to be working for more than 1 min.

Considering the impact and nature of the problem I find it strange that Samsung didn't issue any revert on their update. We have many other users in the organization who are also forced, due to corporate policy, to update their phones but not everyone is having the same issue. So issue seems to be very isolated to particular phones or specific apps. Considering that phone behaves in a similar way even when being run in Safe mode I suspect that issue is related to internal SW developed by Samsung and not some 3PP apps that I have installed.

Our corporate IT department is unable to troubleshoot this problem so only options that I have is either to wait for Samsung to acknowledge the problem (they already did it for some reboot issues but I'm not 100% if I'm having the same issue) and release a fix/revert or just get a new phone and try to migrate my data there hoping that new phone won't have same issue. My personal files are backed up as well as corporate data. So at the moment my main concern is not loss of data as such but time and effort that need to be invested into migration process without any guarantees that it won't be wasted time. Not everyone has an access to a spare phone and time to fiddle with migration. Where are the guarantees that new update won't cause same issue!?

In general, this is extremely concerning when SW update can more or less "brick" the phone or at least cause huge impact on professional and personal life of the users.

I hope that Samsung and other manufacturers will start separating actual important stuff (like security updates) and gimmick (like new One UI interface update that caused issue for me). It's fine! Phone is fine! It worked fine from "day one" and I just want to have it working. The less you fiddle with it - the more stable it will be. Unfortunately, all users are forced to install all features (including new ones). Often it works fine but sometimes it fails. When it fails it would very helpful to be able to revert the change or be able to troubleshoot the problem. Currently I don't have a clue why my phone is restarting all the time and I can't prevent this from happening.


I’m one of huge amount of people suffering with issues since the Android 13 update.  My S21 has been randomly turning off and on since the update.  I’ve done all the suggested “fixes”, even had a Samsung Doorstep appointment, where a qualified Samsung technician looked at the phone, identified software issue, told me it “should” be fixed…..and it’s continued to reboot.  Admittedly since last Friday, it doesn’t appear to be doing it as frequently, maybe once/twice a day as opposed to five or six.   Mine also got stuck in a reboot loop but I just kept pressing the volume down and the other side switch and managed to get the phone back on.

I’ve been advised that Samsung are acknowledging that this update has affected a large number of users and they are working urgently with Google to push a fix out.  How quickly this will actually be is anyone’s guess. 

Is the phone inside a protective case and high spec?

I had this with a sturdy plastic/rubber case and which was the cause of this issue for me. Simply shutting down from overheating. Especially with heavy use or charging, or even randomly hot phones reported since also.

Phone has "Samsung spec". I don't know if S21 5G considered being high spec model or nor. Especially when this is changing every day with new product releases.

In day-to-day operations I do use a phone case as it's required by my company.

I have tried to remove my phone from the phone case but it was still behaving the same way.

I have tried to put som freeze pads around it but it didn't help.

I have tried to put it into a bucket with ice cold water but it was still rebooting.

Considering that phone worked perfectly fine in the phone case for the last almost 2 years I don't think it's the one causing the issue. But thank you for your advice.

First Poster
My s20 ultra 5g is same looping the 5.1 update even though its showing complete. How do we fix this prior to this update my phone has never had an issue now this phone runs slow an update pops up randomly all the time.

Still no reply from Samsung... That's really disappointing.

I got tired of waiting so I decided to do factory reset on my phone. As I'm using Corporate Android version it requires me to connect to the network (WiFi or Cellular) in order to "activate" my phone. During the setup process after language selection you have to do that. As soon as I connect to the network - phone again jumps into reboot loop. So even after reset I can't use the phone.

I got tired of waiting for reply from Samsung so I had a possibility to exchange my broken phone for a different one (same model, but new). Despite running the same version of software it seems to be stable (knock on wood). After that I tried to restore my phone from a backup that I previously created and that suggested by @Libb only to find out that A LOT of things were not part of that backup. I have lost several apps. Those apps that were downloaded back had no settings preserved in them. So all login information, all history - all gone... Most devastating was loss of Google Authenticator data. So even you do regular backups, make sure to go through your every app to see if there are some extra steps needed to be taken to properly save everything.

So backup was useless and support is terrible. I'm very unhappy Samsung user and I would probably not choose Samsung as my next phone.

First Poster

Unfortunately this is an issue that has made my favorite phone  completely unusable. For those of us still hoping for a fix I just wanted to say that factory resetting does not fix this problem.

It actually makes things worse, or at least in my case since all of the data I had just backed up was glitched out of existence when the one ui 5 update came up as the phone was restarting.  


This is planned obsolescence from samsung, take them to court, only way they will learn. They got fined for millions for this in Italy. Slimy sly g**s