Intermittent “Failed to register DLL data” when starting EO.WebEngine after app idle

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dayers

Posted: Tuesday, February 17, 2026 12:32:14 PM

Rank: Newbie
Groups: Member

Joined: 2/17/2026
Posts: 3

I’m running into a strange intermittent issue with EO.WebBrowser in a WPF application (.NET 8).

Very rarely, I get the following exception:

Quote:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.Exception: Failed to register DLL data.
at EO.Internal.xeym.rcvg.evav(Type[] nrl, xeyo[]& nrm)
at EO.Internal.xeym.qqkd(Boolean& nmu, Type[] nmv, String nmw, String nmx)
at EO.Internal.xeym.lwry(Type[] nmr, String nms, String nmt)
at EO.Internal.xeyn.lwry(String nsj, String nsk)
at EO.Internal.uxnc.uptr()
at EO.Internal.uxnc.fxro.avnn()
at EO.Internal.xeuc.qdnb(Action lvb)
at EO.Internal.uxnc.kglc(WindowsIdentity hi)
at EO.WebEngine.Engine.Start(WindowsIdentity user)
at EO.WebEngine.Engine.Start()
at EO.Internal.uxnc.uptq()
at EO.Internal.qthw..ctor(WebView d)
at EO.WebBrowser.WebView.Create(IntPtr hWnd)
...

What’s strange
The app launches fine. If I do not wait and go straight to launching the EO browser code there is very rarely any issue.
EO browser functionality works normally.
If I leave the application idle for ~5–10 minutes without interacting with any EO browser components, then try the execution, the exception consistently occurs.
Once it starts happening, I must close the main app via task manager.

It appears to be failing during: EO.WebEngine.Engine.Start()
Specifically with: System.Exception: Failed to register DLL data.

Possibly related to Engine lifetime / delayed initialization ?

Questions

What exactly triggers “Failed to register DLL data” inside EO?
Could this be related to Windows identity or session changes after idle?
Is it recommended to explicitly call Engine.Start() at application startup instead of lazy-starting on first WebView creation?
Are there known issues with EO after long idle periods?

Any insight would be greatly appreciated especially if someone has seen this pattern before.

eo_support

Posted: Tuesday, February 17, 2026 1:24:11 PM

Rank: Administration
Groups: Administration

Joined: 5/27/2007
Posts: 24,467

Hi,

Can you clarify which of the following 2 situations is your situation?

1. Start your application and use EO.WebBrowser code (which works fine), then wait for 5 to 10 minutes, then use it again, then it fails;
2. Start your application, never use EO.WebBrowser code, wait for 5 to 10 minutes, then use EO.WebBrowser code for the first time and it fails;

Thanks!

dayers

Posted: Tuesday, February 17, 2026 1:29:02 PM

Rank: Newbie
Groups: Member

Joined: 2/17/2026
Posts: 3

Hello,
It is situation #2 for me.
I would like to note this happens on the newest version as well as the version I first detected it in (25.2.1)

eo_support

Posted: Tuesday, February 17, 2026 4:16:04 PM

Rank: Administration
Groups: Administration

Joined: 5/27/2007
Posts: 24,467

Hi,

This might be a low memory situation. EO.WebBrowser requires a large chunk of continously memory block when it first initialize. This usually is not an issue when application just starts. However after the application has been running for a while, it's memory space can become fragmented to the point where such large continous memory block no longer exist. This would cause EO.WebBrowser fails to intialize.

However our past experience is when this occurs the code would fail at a different location with a different stack trace. We have not seen this particular stack trace for this reason before. As such if there is anyway to reproduce this problem or if you can provide a test system that we can access remotely it would be very helpful for us to get to the bottom of this issue.

Thanks!

dayers

Posted: Tuesday, February 17, 2026 4:47:35 PM

Rank: Newbie
Groups: Member

Joined: 2/17/2026
Posts: 3

I will see if your request is possible to complete.
However, I have seen this issue occur even after start up even without waiting, just with much less frequency. It just seems that waiting will definitely trigger the hang.

We have seen instances of installing the app and immediately running into the hang, and sometimes it never happens at all, it has been very tricky to reproduce until I accidentally discovered leaving the app idle also triggers it.

I also have what looks like an encrypted Webview*.txt crash file I cannot understand.

Just to also be sure, .NET 8 is fully supported/compatible?

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