Warnings generated through a CustomAnalyzer are being displayed twice in the Error List Window

[YakupIpek21]

Describe the bug
After having defined a CustomAnalyzer and added the project containing the custom analyzer as a reference to wpf-project the warning is displayed twice in the Error List Window when saving the xaml-file.

To Reproduce

1. Use the project template to create a custom analyzer.

2. Adjust the auto-generated analyer by changing the TargetType Property to TextBox

3. Create a wpf project (.Net Core 3.1) in the very same solution

4. Enable Custom Analysis in Visual Studio

5. Add a TextBox without any attributes and save the file, a warning should be displayed
   

6. Add a space within the opening tag of the TextBox and save the file again, now the warning is displayed twice
   

7. Deleting the space and saving again does not reduce the number of warnings

Expected behavior
Warning should be displayed once in the Error List Window