S21 ultra restart issues and poor connectivity after one UI 6.1 update

[Nomeking]

Hello Everyone,

I recently encountered a serious issue with my Galaxy S21 Ultra after i updated to One UI 6.1 on June 22, 2024. Since the update, the automatically restarting randomly upto 10 times a day. I can't interact with my device at all. Sometime it reboots in the middle of important tasks, phone calls inclusive.

To troubleshoot, I have tried wiping the cache partition and even performed a factory reset 4 times, downgrading back to One UI 6. Despite these efforts, the phones still restarts randomly most times with reboots and poor network connection. To make matters worse the moment I get invalid network notification phone is unresponsive and restarts automatically. 

The phone is only 5 days old and it's very annoying to have to encounter such when the device is new.

I'm at a loss and would greatly appreciate any advice or solutions from the community. Has anyone else experienced this issue? Are there any additional steps I can take to resolve this?

If possible is there a way of downgrading to one UI Version i had when i first bought the phone?

Samsung please respond here!

Thank you in advance for your help!

[Sky4ll]

It's strange. My S21 Ultra was also updated with the 6.1.1 and June security patch. It is fine. No problems were experienced after the updates..

[Nomeking]

Samsung has messed me up on this one.i literally can't use the phone

[Neolyn]

I think the problem is your Galaxy S21 Ultra battery. As the device was released in 2021 which could be the reason since the battery has been degrading and you said that it is 5 days old.

Can you please state if you bought it in a sealed box or second hand.

[Nomeking]

I bought it in a sealed box from Los Angeles USA. I recently bought on ebay and I received it on the 21st of June 2024

[Neolyn]

Can you please do me a favour. I want you to please follow the following and please reply with a screenshot.

Go to settings

Settings > About phone > Battery information.

[Neolyn]

I do not see it.

[Neolyn]

I do not see any issues with the battery.

You have said that the phone restarts when you get an invalid network notification. Is this when connecting to WI-FI or using Cellular network?

[Nomeking]

Both but especially cellular network. Network just cuts off and the moment it says no network phone can restart today for example it's 15 time's. Am recording the number of times

[Nomeking]

Am actually using my A51 device to respond on this thread to take a screenshot I had to perform 5 wipe cache partition and send on my s21 ultra but even now the phone is still switching on and off