The bug report is declined due to a lack of information. Further details about the issue were not provided.

Regards,
Martin
Progress Telerik

Hi Mauro,

Thank you very much for the runnable example provided. 

From what I understood from your question, you are currently utilizing the Kendo UI for Angular Master-Detail Grid together with the virtual scrolling and grouping functionalities and are experiencing some undesired behavior of the component while expanding and scrolling the detail rows. Please, correct me if I misunderstood you.

I have thoroughly examined the provided code in the StackBlitz demo and indeed noticed some unexpected behavior of the Grid during the mentioned user interactions. What I would recommend as a potential resolution would be for the developer to use the GroupBindingDirective to handle the data binding of the Grid: 

https://www.telerik.com/kendo-angular-ui/components/grid/scroll-modes/virtual/#toc-virtualization-with-grouping'

Furthermore, since the Master-Detail Grid is being utilized, the developer would need to make sure that its detailRowHeight property is set as it is crucial for some internal calculations of the component which ensure the proper behavior of the virtual scrolling with such types of Grid. For further reference, please check out the following article: 

https://www.telerik.com/kendo-angular-ui/components/grid/scroll-modes/virtual/#toc-getting-started 

For your convenience, I modified the provided StackBlitz example so that it implements the suggested modifications and it seems to me that this resolves the undesired behavior: 

https://stackblitz.com/edit/angular-5elhtu-c3sree

I hope this helps. Please, let me know if I am missing out on something.  

Regards,
Georgi
Progress Telerik