I'm afraid we are unaware of such issue and I could not reproduce it on our end.
Could you please let us know what leads you to believe the RadRichTextBoxStatusBar causes the observed error? Additionally, is the error observed when running the project or when interacting with one of the controls in the view?
What I'd suggest is to check whether all referenced Telerik assemblies are the same version. You could also try cleaning and rebuilding your project.
Let me know how it goes.
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