Thank you for reporting these issues.
I was able to reproduce them. The first one is caused by the protection against the overflow of the buffer queue for the layout. Currently, I cannot provide you with a workaround for it. As far as the second one is concerned, please add this piece of code in the Form_Load
|this.radTabStrip1.TabStripElement.TabLayout.ItemsOverlapFactor = 0;
Both issues will be addressed for one of our future releases. I updated your Telerik points for the report.
If you need additional assistance, do not hesitate to contact me.
the Telerik team