Mail app stuck in loop accessing ShaderCache file

[DoctorRashir]

I have an issue where my Mozilla ThunderBird email app seems to be stuck in a loop repeatedly accessing a file in the Shader Cache, filename:

C:\Users\MyUser\AppData\LocalLow\Intel\ ShaderCache\4a5eb0e65e559fc08e65ecb2fa9d650817ae895582a7a7ede162866d3e47a05a

For weeks, I have been trying to solve it by posting in the Mozilla help forums, but haven't found a solution. So I'm posting here in the hope I can find a solution.

I know TB is looping on the ShaderCache because I've captured a Promon trace of this. When TB is running normally, it will access the ShaderCache periodically for a short time. But randomly, the app will loop accessing the ShaderCache for a very long time. Like 30 minutes or longer. Sometime it breaks out on its own, other times I have to exit the app.

Uploaded is an Excel WB of the stack trace of the three ProcMon events that capture the loop. These three events repeat. Until the app breaks out of the loop.

Given the limits on my knowledge of Promon and Thunderbird. I can't determine anything further. I can provide the trace file (securely, of course) if that is helpful.

The setup:
Windows 11 on a custom system running an Asus H670-Pro motherboard. I am using the onboard graphics, Intel UHD 770. (I don't play games)
All Windows updates installed. Updated to latest Thunderbird. Cleared caches and rebuilt email indexes.
Per suggestions on the Mozilla forum, I have updated the graphics driver. Cleared and deleted all cache files I could find.

Any guidance or direction is greatly appreciated.

[Diego_INTEL]

Hello @250526,

Thank you for contacting Intel Embedded Community.

I have been checking this, if the issue may be associated to graphics, maybe you can try uninstalling the Intel's Graphics driver. There could be an incompatibility or some bug, but maybe this can help to know if the driver is causing this issue.

Best regards,

@Diego_INTEL

[DoctorRashir]

Thank you for your reply and suggestion. 

When I started this thread I was running UHD 770 Driver Version: 32.0.101.6737 Date: 4/16/2025. This was the latest that MS was installing. Now I have updated to the version from Intel: 32.0.101.7026 Dated: 8/19/2025. I selected a Clean Install.

So now I'll have to run this for awhile to see if the issue occurs. I also noticed that in Procmon, Thunderbird queries a registry key: HKLM\SOFTWARE\Intel\Display\igfxcui\3D\ShaderCacheForceDisabled Result: NAME NOT FOUND. Is this something I can flip so TB doesn't use the ShaderCache? Would this affect other things on my system?

Also that three event loop still happens periodically but only for a very short time. It seems to happen when TB wakes up and checks for new email.

[DoctorRashir]

After mulling this over some more, I think is it more likely that the issue is with Thunderbird. The process and thread that is accessing the ShaderCache is the one that seems to be key to handling the details of displaying the UI. If I suspend that thread, the whole window freezes.

So, thank you for taking the time to reply. It's off to pursue Thunderbird some more.