S21 Ultra One UI 4 - Mobile Connection Issue

[djang0U]

I have been using S21 Ultra with Singtel 5G since early this year, and had no issues whatsoever.

After upgrading to One UI 4 on 28 Nov 2021, I have been experiencing severe nonstop mobile network disconnection and mode switching issues on a daily basis.

Below are the details.

1. 5G kept switching to 4G+ and back for no reason.

2. When using YouTube or browser or any app, 5G will suddenly switched to 3G or H+ (which I have never experienced before), and stay at 3G and H+ for more than 10mins.

3. Mobile service completely cut off for no reason. (Happened twice).

Below are what I have tried but still cannot resolve.

1. Reset network settings

2. Switched off VoLTE on SIM 2

3. Reboot into Safe Mode (guided by Samsung Online Chat)

4. Took out Singtel 5G SIM and put into another Android phone to prove nothing wrong with Singtel service.

5. Emailed to Samsung support. But no reply.

My advise to anyone dying to upgrade to One UI 4... Don't!

If anyone has workable suggestions, I'm all ears.

Thank you.

[sai_virinchi]

I'm the same issue, any solution? @Samsung?

[djang0U]

One UI 4.1 is on its way... hopefully it can resolve most issues...

[sai_virinchi]

Did anyone take this issue to the service center?

[djang0U]

Yes. I did. The staff have no clue what is going on. Even suggested factory reset. Amazing isn't it...

[zy_zyzy]

Exactly the same issue with Z Fold3 after updating to One ui 4. Mobile connection breaks too frequently, jumping from 5G to 4G non stop, or frequently showing the no connection sign. Cannot rely at all especially with Samsung pay.

Do not update to one ui 4. Not worth it.

[sai_virinchi]

There should be an option to revert back the update for every phone manufacturers!!

[ziki77]

Same USB tethering performance issue after updating my S20 5G to ONEUI4, I tried to force 4G only mode but it does not fix the issue. I do not want now to perform a factory reset...

Very frustrating....

[djang0U]

Don't bother with factory reset. I've tried it, does not work!

[Ionisedatom]

You can report the error at Samsung members and send them a system log within 15 minutes of occurrence of issues. Use wifi to send the error report. I'm doing this too. Same thing happening. By this they will know and try to fix. 

[djang0U]

I have already perform this reporting in December 2021. Samsung replied "No solution avaliable and working on it"