Hello Christian,
Thank you for your feedback.
If you are referring to the RadTabControl, you can set its IsContentPreserved property to True. This way the control will keep its content state and changing the selection will not load/unload the tab's content.
Regards,
Vladimir Stoyanov
Progress Telerik
Hello Christian,
Thank you for taking the time to isolate this issue in a sample project.
I can confirm that I was able to replicate the degraded performance at my end and will thus log this issue in our internal backlog. As a thank you for bringing this to our attention, I've awarded you with some Telerik points.
Please follow this bug report to get notified about any changes in its status.
Regards,
Dilyan Traykov
Progress Telerik