Tooltips rapidly close - existing WPF 4.8 application - some computers only

[DaveInCaz]

Description

This problem is specific to certain PCs, and I am looking for advice how to narrow down the cause. The problem has emerged for an existing compiled WPF 4.8 application, seemingly triggered by certain system updates.

Problem: certain Tooltips will rapidly flash on/off. This is similar to other tooltip issues here but none were for .NET Framework 4.8. (#7489, #6710, #6852, #6289, #6220)

In one example we had a user whose PC was updated from Windows 10 to 11; no problem before the update, problem occurs after the update. Something relevant must have changed -- but what?

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I will gladly add any additional information about my application or system details that might be useful. But I'm not sure what to do next to figure that out.

Reproduction Steps

My application consistently shows the problem on some computers but I have not yet been able to create a small repro that also does so.

On PCs with this issue, when the user mouses over certain custom controls (derived from Control) the problem happens. Other controls have no problem.

Expected behavior

Tooltip remains visible.

Actual behavior

Tooltip briefly appears/disappears.

Using WPF Snoop the following events all are logged at the same moment:

Regression?

Yes

Known Workarounds

None

Impact

We use the tooltips to summarize some info that the user otherwise can only access with many more steps.

Configuration

System info... may or may not be relevant:

From computer C without the issue:

• RuntimeInformation.FrameworkDescription = ".NET Framework 4.8.4739.0"
• System.Environment.Version = "4.0.30319.42000"
• OS Name Microsoft Windows 10 Enterprise
• Version 10.0.19045 Build 19045

From computer D with the issue:

• RuntimeInformation.FrameworkDescription = ".NET Framework 4.8.9277.0"
• System.Environment.Version = "4.0.30319.42000"
• OS Name Microsoft Windows 11 Enterprise
• Version 10.0.22631 Build 22631

From computer J without the issue:

• RuntimeInformation.FrameworkDescription = ".NET Framework 4.8.9277.0"
• System.Environment.Version = "4.0.30319.42000"
• OS Name Microsoft Windows 11 Enterprise
• Version 10.0.22631 Build 22631

Note that D and J are the same so I'm obviously missing some key distinguishing detail.

Other information

No response