Unfortunately I wasn't able to reproduce the issue but I have a couple of suggestions:
- you can set the RadPaneGroup.IsContentPreserved property to True. However, please keep in mind that at the moment this property doesn't work well when the tabs display an HtmlPlaceholder with KeepContentInMemory=True. This is why you can try setting only the IsContentPreserved property to True.
- you can try to set a static size to your HTMLPlaceHolder (something like Width = 300, Height = 300) because in some cases (depending on its parent) it's not able to render itself properly.
If this doesn't help you I'd like to ask you for some code snippets so that we could reproduce the issue.
We're looking forward to hearing from you.
All the best,
the Telerik team