Hello Hadrien,

By default the RadTabControl keeps the state of the currently selected RadTabItem, only. After changing the selection the content of the last active tab is unloaded in order to load the content of the newly selected tab. However, in your case you can try setting the IsContentPreserved property of the RadTabControl to True. By doing this you will force the RadTabControl to keep the content of its items even when they are not selected. For more information you can read this article.

Please give this approach a try and let us know if you have any other questions.

All the best,
Pavel R. Pavlov
the Telerik team