Datagrid virtualization rendering issues

I've added virtualization to the Radzen datagrid on my page.
Everything seems to work fine but for the rendering.
At first I see an empty datagrid.
But when I scroll up and down some items appear randomly.
Has anyone experienced a similar effect and know what the cause is?
Without virtualization the data shows up fine.
Thnx in advance

I think you must define a "Height" in the datagrid for virtualization. E.g. 400px

Hi Thomas
Thanks voor your reply.
I already did that. After that I did see a scroll bar. And the count shows that data has been loaded.
But as mentioned, the datagrid appears empty. Until I scroll up and down. And then I randomly see some items scrolling by. And they disappear again when I stop scrolling.
I display the item count on the page and I can see that the LoadData event is triggered and new data is being fetched when I scroll up and down.

Ahh stupid stupid. I found out what the problem was.
I switched the Skip and Top values in the query.
If you ever wish to enrich you pages with confusing inexplicable datagrids, this is the way to do it.