How to fix APC_INDEX_MISMATCH and IRQL_NOT_LESS_OR_EQUAL on my Windows 11 pc.

Question

How to fix APC_INDEX_MISMATCH and IRQL_NOT_LESS_OR_EQUAL on my Windows 11 pc.

Burning Attack 0

Hello, I've recently been encountering a lot of BSOD on my Windows 11 pc and I've been wondering how to fix it? I would post my minidumps but the website won't allow me to. it claims its the following thread:

For IRQL_NOT_LESS_OR_EQUAL is the first one

For APC_INDEX_MISMATCH is the second one

FAULTING_THREAD:  ffffcb06d3892280

FAULTING_THREAD:  ffffa00f57754080

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Answer 1

Francisco Montilla 31,090 Independent Advisor

Hello!

Those hex addresses for the faulting threads unfortunately do not tell which exact driver or process is actually tripping the system to crash. Since the forum will not let you attach files directly to your post, you will need to share the minidumps using OneDrive so I can get a proper look at what is happening under the hood.

Go to C:\Windows\Minidump and copy all the files in there over to your Desktop first so you do not run into any annoying file permission errors. After they are on your Desktop, drop them into your OneDrive, click to share them, make sure the access is set so anyone with the link can view them, and paste that share link back here in a reply.

Once you get that link posted I can pull the files and run them through the Microsoft debugger to find out exactly what module is causing your bluescreens.

Burning Attack 0 Reputation points

2026-10-07T21:37:40.44+00:00

Does this work? https://1drv.ms/f/c/e20810a2bf50e73b/IgCgF4fwlz-1SLoZ4paGsz8SAVyKw0t4szuTA1RoNb7LH_I?e=970q5u
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-07T21:39:41.7966667+00:00

Hey! I can see the folder, but it is empty, did you upload the dumps just yet?
Burning Attack 0 Reputation points

2026-10-07T21:47:28.7733333+00:00

hello it should work now https://1drv.ms/f/c/b90700fe9b9fe525/IgD3HNKAfu_VSb0qPvAirBg_ARh9eocoqKr_foNMJcuZwDc?e=CUnXMD
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-07T22:00:01.33+00:00

Okay. I looked through the minidumps and the errors are bouncing around between a few different things. One crash is directly pointing to the Urban VPN app, another points to Wallpaper Engine, and one of the others points to your storage driver.

When the errors are scattered across different apps and system drivers like this, it typically points to a low level driver conflict or bad RAM rather than a single app being broken.

Did these blue screens start happening right after a recent Windows update or did you install any new parts in your PC lately?
Burning Attack 0 Reputation points

2026-10-07T22:05:15.05+00:00

I had a recent error where my windows file explorer wouldn't activate and I couldnt click anything on my pc so I went to my bios and loaded the optimized defaults and it fixed the windows file explorer but then the blue screens started happening, I haven't installed any new parts in my pc either and I just recently upgraded to windows 11 to stop the crashes from happening
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-07T22:11:09.72+00:00

That timing makes sense. When you loaded optimized defaults in the BIOS, it reset all hardware profiles, and memory instability often shows up right after BIOS changes as random crashes across different processes.

The best step right now is to test your memory for corruption.

Press Windows + R, type mdsched.exe, and hit Enter. Choose the option to restart now and check for problems. Let the Windows Memory Diagnostic run fully and see if it reports any hardware errors when your PC boots back up.
Burning Attack 0 Reputation points

2026-10-07T22:13:06.9666667+00:00

I did that after installing windows 11 and I didnt get any memory errors
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-08T00:26:51.7766667+00:00
Okay. Then let's go for the usuals, check for corrupted Windows system files that might have carried over from the upgrade. Press Windows, type cmd, right-click Command Prompt, and select Run as administrator.

Type this exact command and hit Enter:

DISM.exe /Online /Cleanup-image /Restorehealth

Once that finishes, type this command and hit Enter:

sfc /scannow

Let both scans complete, restart your PC, and see if it finds and repairs any damaged files or if the blue screens keep happening.
Burning Attack 0 Reputation points

2026-10-08T03:28:15.14+00:00

so far it said this Beginning verification phase of system scan.

Verification 100% complete.

Windows Resource Protection did not find any integrity violations.
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-08T03:38:03.02+00:00

Okay, that rules out broken system files. Now looking back at your first dump, try uninstalling Urban VPN completely from your PC for now. Go to Settings > Installed apps > Urban VPN, and uninstall it. Restart your PC afterward and use your computer normally to see if the crashes stop.
Burning Attack 0 Reputation points

2026-10-08T03:51:22.26+00:00

hello, it crashed again, here's the dump https://1drv.ms/f/c/b90700fe9b9fe525/IgBFA55OD4lnTY5dbLOEXMTVAesBbkn1W4iAfQjF6U__uf0?e=VkYwzF
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-08T03:56:54.2233333+00:00

This dump crashed inside opera.exe. Again trying to read a null memory address directly inside the core Windows kernel scheduler.

I still think seeing crashes jumping across Wallpaper Engine, your VPN, opera.exe, and storage right after loading BIOS defaults strongly points back to memory timing or profile settings, since the built-in diagnostic test can miss subtle timing errors.

Reboot into your BIOS setup. Check your memory configuration to see if XMP, DOCP, or EXPO is currently disabled or enabled. If an XMP/DOCP profile is off, try turning on Profile 1, or if it is already turned on, try toggling it off to run at stock baseline speed. Save the changes, boot back into Windows, and test if the blue screens keep happening.
Burning Attack 0 Reputation points

2026-10-08T06:49:01.73+00:00

I did what you said and it ran fine until I got hit with this crash https://1drv.ms/f/c/b90700fe9b9fe525/IgD5UPy0EP_iQZx6ZOlqe_3aATBvyWTlNVua-80PC82KOvw?e=nzK72X
Burning Attack 0 Reputation points

2026-10-08T21:36:24.3833333+00:00

I don’t know what it could be I haven’t turned on my pc out of fear of more crashes
Burning Attack 0 Reputation points

2026-10-09T02:12:48.33+00:00

Hello I turned on my pc and I received about 5 different crashes and it was really difficult to boot back into my pc it was a pain and it even showed me a boot error because it would not start up so I was forced to force reboot
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-09T03:04:14.4366667+00:00

Yes, this is almost always a physical hardware fault with one of your RAM sticks. Software memory tests like mdsched routinely miss unstable memory cells, but running the PC like this will slowly corrupt your Windows installation and personal files.

The single best step right now is to isolate which RAM stick has gone bad.

Power down the PC completely, unplug the power cord from the wall, and open the case. If you have two sticks of RAM installed, take one stick out so only a single stick remains in the recommended primary slot.

Plug it back in, turn on the PC, and see if it boots smoothly without any crashes. If it still crashes or fails to boot, swap it for the other stick. This will tell you immediately which stick is causing all the failures.
Burning Attack 0 Reputation points

2026-10-09T07:53:09.1266667+00:00

Hello, I tried this and both failed https://1drv.ms/f/c/b90700fe9b9fe525/IgDALGNTbo5lSKuiCywzdrZVAWJhK-VSgK6Pzcz76IVG-OU?e=fMJZju
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-10T01:18:56.0166667+00:00

Hmm, it is extremely rare for two RAM sticks to die at the exact same moment. That usually points to either the specific motherboard slot being faulty, an issue with the CPU or motherboard itself, or your SSD failing, especially since one of your earlier crashes was in the storage driver.

To narrow down what is going on, did you test both sticks in that exact same slot, or did you try another slot as well?
Burning Attack 0 Reputation points

2026-10-10T01:20:21.85+00:00

I tried both in the same slot as you indicated
Francisco Montilla 31,090 Reputation points Independent Advisor

2026-10-10T01:21:49.7233333+00:00

That is really helpful to know. If both sticks failed in that exact same slot, there is a good chance that specific slot has a bad contact or that memory channel is having issues, rather than both of your RAM sticks dying at the exact same time.

Take just one of the sticks and try it in slot 4 instead, which is the slot furthest to the right away from your CPU. If your motherboard only has two slots total, just put it into the other open slot. Turn the PC back on and see if it boots up cleanly into Windows without throwing any errors.