Unfortunately I'm not sure if we could help you based only on the attached picture. It'll be great if you could send us a sample project that reproduces this behavior or at least some code snippets to show us how you use the RadTileView and what is the content of its items.
At the moment a possible problem that I could think of is if for some reason the RadFluidContentControl measures all three of its contents on start up and this causes the delay.
Another possible problem is if your ColumnWidth/RowHeight are set to Auto and the content of you RadTileViewItems need a couple of measure passes to define their sizes.
On another hand the measure time depends on the complexity of the content of the items and the their number. When an item measures itself it measures the whole hierarchy of its children and that may take some time.
We're looking forward to hearing from you.
All the best,
the Telerik team
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