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!
The network issue not just happen to S21s and Z 3 series, but happened to my new S22 Ultra as well. So the problem obviously is not from phone but from the One UI 4 software itself.
I have not encounter any issues when my Z Fold 3 running on One UI 3.1 previously.
Also factory reset did not help either. (This includes partition cache wipe)
I have tried factory reset my Z Fold 3 after One Ui 4.1 update. It works for a while, but then the problem came back. The frequency of data connection drops is less frequent than the One UI 4 though.
