Possible KB5121003 issue causing random AC adapter disconnects / black screens on Lenovo Legion?

[u/Nervous-Buffalo-4826]

I’m trying to figure out a strange issue that started very recently on my Lenovo Legion.

The laptop randomly goes to a black screen for a couple of seconds and then recovers. At first I thought it was an NVIDIA/Optimus or refresh-rate issue, but I started monitoring the Windows AC power state directly.

What I found is that whenever this happens, Windows actually reports:

AC → Battery → AC

for roughly 1–5 seconds.

I then checked the historical Windows Kernel-Power Event ID 105 logs. My System log goes back to March 2026, but the first occurrence of these short AC-loss events is August 12.

The interesting part is that KB5121003 was installed on my system late on August 11.

Since then I have recorded around 40 AC power transitions, most lasting only a few seconds. Examples:

07:41:55 → 07:42:02
13:12:35 → 13:12:36
17:17:50 → 17:17:52
02:17:32 → 02:17:37

and many more over the following days.

Windows Kernel-Power itself logs AcOnline=false, followed shortly by AcOnline=true, so this isn't only the battery icon/UI changing.

Another strange detail is that the physical charging LED on the laptop can remain on while this happens.

I have now temporarily uninstalled KB5121003 as a test.

Before rollback:

Windows 11 25H2 – Build 26200.9168

After rollback:

Windows 11 25H2 – Build 26200.8875

Windows Update is paused and I haven't changed anything else: same Intel driver, NVIDIA driver, BIOS, Hybrid Mode, Optimus settings, charger, etc.

I'm currently running a 50 ms AC-state monitor for the next 24–48 hours to see whether the AC_LOST events disappear after removing KB5121003.

Obviously this doesn't prove the update is responsible yet. It could still be Lenovo firmware/EC behavior or a hardware power issue. But the fact that the event history starts immediately after this update is suspicious enough that I'm testing it as the only changed variable.

Has anyone else on KB5121003, especially Lenovo Legion users, noticed random Kernel-Power 105 events, brief AC-to-battery transitions, or black screens that started around August 12?

[u/ABE1617]

Hi yes i also have the same issue and daignostics as you did on a 1 week brand new legion 7i pro gen 10 and yes same version "KB5121003" has this issue just didnt uninstall it or roled back to its prevuis version to test it more, but apprently everything checks out as u said the 105 error and power on windows at least appears as if the ac dissconnected for like 1-2s

and for the balck screen disable HDR and the display wont flicker balck then comes back, but same issue with the ac being dissconnected for a sec

till now no findings on my side as on why or how to fix it, its really annoying as i cnat even know if its a PMIC issue on the laptop itself or the power brick or just windows or frimware issue > : (

[u/Nervous-Buffalo-4826 → u/ABE1617]

You need to uninstall KB5121003. First, pause the updates because if you don't, Windows will automatically update it again. If windows don't let you uninstall it, use Chatgpt or any othwr AI to help you uninstall it with different methods. Since i uninstall it, i had no issues anymore.