New Stable One UI 4 Update Addresses Galaxy S21 Lag Issues

Samsung Galaxy S21 Ultra AH 02

Samsung started rolling out the Android 12 One UI 4 update for the Galaxy S21 series a few weeks ago. While it was time for the Galaxy S21 series owners to rejoice, users in the USA started facing lag issues on their handsets after updating their Galaxy S21 series phones with this new Android 12 update.

Several Samsung Galaxy S21 users in the USA reported lag issues on their devices after installing the Android 12 update on Reddit. Thankfully, other regions weren’t affected by this problem.

However, USA users were experiencing UI stutter and lag issues, affecting the overall user experience of the phone. The good thing was Samsung recently acknowledged this issue plaguing some Galaxy S21 devices.


In line with this, finally, a new Android 12 One UI 4 update is rolling out for the Galaxy S21 series phones that apparently fixes the lag issues. The issue started popping up when users selected 120Hz in Settings.

The UI would go back to a 60Hz refresh rate once the user stopped touching the screen. This resulted in stuttery animations, scrolling, and UI lag.

The Galaxy S21 hotfix update arrives with software version G99xUSQU4BUK9

If you have a Galaxy S21 device in the USA that is affected by this lag issue, then the update should be live for your phone. It arrives with software version G99xUSQU4BUK9.


Here, the ‘x’ stands for different models of the Galaxy S21 devices. This includes the Galaxy S21, Galaxy S21+, and the Galaxy S21 Ultra.

This new One UI 4 hotfix update bumps the software version from G99xUSQU4BUK7 to G99xUSQU4BUK9 on the US carrier models. Notably, the update is rolling out gradually for users in the USA.

As of now, the update is showing up for Verizon models. We expect the update to reach other carrier models in the coming days very soon.


There is no clarity on whether the update will be made available for other regions or not. According to GSMArena, users who installed this new update are already experiencing overall improved responsiveness on their phones.

The official changelog doesn’t mention the UI stutter bug, but the improvement is noticeable. Some third-party apps are still suffering from scrolling lag. If you haven’t received the update notification, then you can manually check for it.

To do that, simply head over to the Settings menu. Then tap on System updates and select Download and install. The system will check for new updates, and once detected, you can tap on the notification to begin the download.