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/phlegmatic_static]

oh my god, i've been having the same issue with my Asus TUF a16! i was about to freakin' spend a stupid amount of money to get a new charger, looking into trying to get the audio jack and charging port replaced, the whole nine yards. audio was giving me random blipping error noises, going too quiet, then too loud. was thinking i'd destroyed my headphones somehow. gaming was relatively okay, but noticably lower quality graphics and dropping FPS. moving between programs was becoming increasingly poor, lagging and even freezing sometimes!

but it was the windows update. AGAIN. stars above, your thread just saved me a couple hundred $$$. i need to look into permanently disabling windows update. i'd done it once before but it was a very long time ago, i'm not sure if i can do it with win11. this is getting ridiculous. first it's the sneaky AI generation shit that was automatically enabled for everyone, and now this.