Zygisk causes screen flickering on Galaxy Tab S7 FE (SM-T733)

[muhep06]

Device: Samsung Galaxy Tab S7 (SM-T733)
Android version: 14 (One UI 6.1)
Magisk version name: 427a1ca
Magisk version code: 28104

Description of the issue

When Zygisk is enabled (with no modules), the screen begins to flicker continuously on both:

• The device's own display
• External monitors via USB-C to HDMI

The flicker is not visible in screen recordings, but it is visible by eye on the physical screen.

As soon as Zygisk is disabled (Magisk still installed), the issue disappears completely.

Steps to reproduce

1. Install Magisk debug build 28104
2. Enable Zygisk (without installing any modules)
3. Reboot
4. Observe flickering on device screen

Attachments

• magisk.log (from debug build) magisk_log_2025-05-11T23.35.31.log
• Video showing the flickering issue directly from the device screen Video

[muhep06]

Additional discovery:

Enabling "Disable HW overlays" in Developer Options completely stops the flickering issue.

[mapleLeafOfficial]

nice , good idea

[mapleLeafOfficial]

The failed HW peak layer will be automatically closed every time the phone is started. You can use the "Turn on Vulkan and system optimization" module to replace HW with Vulkan to solve this problem. It has been tested and is effective. The module URL is https://apk.magisk.vip/app.php?id=539 （Now I find that this method doesn't work）

[muhep06]

It didn't work for me. I enabled Zygisk and the flickering started. I installed this module and rebooted, but the flickering is still happening on my tablet. Whenever I enable Zygisk, the flickering starts. Honestly, I can't make sense of it.

[mapleLeafOfficial]

Well, the screen flashed suddenly when I was watching it just now, but if you turn off the HW overlay, this problem will not occur. I'm sorry, I'm now trying to find a module that automatically turns off HW on the phone.

It didn't work for me. I enabled Zygisk and the flickering started. I installed this module and rebooted, but the flickering is still happening on my tablet. Whenever I enable Zygisk, the flickering starts. Honestly, I can't make sense of it.

[muhep06]

Even after installing this module, the renderer still appeared as Skia (OpenGL).
I had also looked for modules that would disable HW overlays, but I couldn't find one that actually worked.

[mapleLeafOfficial]

Hi, friend
I just found out that using the command
service call SurfaceFlinger 1008 i32 1 can disable HW,
so I created a very simple Magisk module that automatically disables hardware overlays at boot time.
⚙️ How it works:
It will repeatedly execute the following command at boot time until it succeeds:

service call SurfaceFlinger 1008 i32 1
This command is equivalent to the "disable hardware overlay" switch.

Even if the system service is not ready immediately, the script will retry several times (with a slight delay) to ensure that it works properly.

✅ Test platform:
Galaxy Tab S7 FE (SM-T733)

Android 14 / One UI 6.1

Zygisk-enabled Magisk v29000
Maybe this script is very LOW QwQ

my_disableHWOverlay.zip

Even after installing this module, the renderer still appeared as Skia (OpenGL). I had also looked for modules that would disable HW overlays, but I couldn't find one that actually worked.

[muhep06]

I managed to get Skia (Vulkan) working, but the stuttering still continues. I'll try your module.

[muhep06]

Hi, friend
I just found out that using the command
service call SurfaceFlinger 1008 i32 1 can disable HW,
so I created a very simple Magisk module that automatically disables hardware overlays at boot time.
⚙️ How it works:
It will repeatedly execute the following command at boot time until it succeeds:

service call SurfaceFlinger 1008 i32 1
This command is equivalent to the "disable hardware overlay" switch.

Even if the system service is not ready immediately, the script will retry several times (with a slight delay) to ensure that it works properly.

✅ Test platform:
Galaxy Tab S7 FE (SM-T733)

Android 14 / One UI 6.1

Zygisk-enabled Magisk v29000
Maybe this script is very LOW QwQ

my_disableHWOverlay.zip

Even after installing this module, the renderer still appeared as Skia (OpenGL). I had also looked for modules that would disable HW overlays, but I couldn't find one that actually worked.

Thanks! This module works perfectly. There’s some stuttering until I enter the password when the tablet first boots, but after startup, I checked and the HW overlay is enabled, and so far I haven’t noticed any stuttering.

[muhep06]

Even when Disable HW overlay is enabled, occasional flickering still occurs. When Knox Patch Enhancer is installed, the flickering becomes more frequent. The only definitive solution so far has been disabling Zygisk from the settings. I can't fully understand why or how Zygisk causes this issue. Honestly, I haven't found a permanent solution yet. Zygisk was an important feature for Knox Patcher.

[muhep06]

I disabled the built-in Zygisk in Magisk and installed ZygiskNext as a module. This solved the flickering issue caused by the built-in Zygisk. I'm able to use Knox Patcher with LSPosed. However, when I install the Enhancer, the flickering returns.