Describe the bug
An error is thrown when a dialog is initialized via the DialogService and the custom content component contains a kendo-dialog-titlebar component in its template.
To Reproduce
Open this demo and click the button to open the dialog.
Expected behavior
The dialog should appear without errors.
Screenshots

Browser
Just ran into this one as well.
Using a custom component, and its template contains kendo-dialog-titlebar.
Confirmed, same issue and repro for my team's product. Breaks a lot of modals since the update to 2020 R3
For the time being, our suggested workaround would be to revert to the previous version - 4.2.2 - until we resolve the issue. Thank you for your understanding.
Fix is available in the latest dev version of the kendo-angular-dialog package. An official version will be released tomorrow.
Most helpful comment
For the time being, our suggested workaround would be to revert to the previous version - 4.2.2 - until we resolve the issue. Thank you for your understanding.