There is a known problem with .NET 9 and hot-reloading. A similar error is displayed in the Output window after the second change.
Change failed to apply (error code: '00-01-00-00-00')
We have reported the issue to Microsoft. It seems to be unrelated to Radzen Blazor Studio - we were able to replicated in a vanilla blazor application created with dotnet new.
Known workarounds:
- Stopping the application and running it again after making the changes
- Installing an older version of Radzen Blazor Studio and uninstalling .NET 9.