Thank you for contacting Telerik support.
I managed to reproduce this case and I have logged it in PITS. Here is the link to it: http://www.telerik.com/support/pits.aspx#/public/winforms/12662
I have updated your Telerik points for this report.
As a workarround I would like to suggest to set the Form's MaximumSize property. For example:
.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
I hope this helps.
All the best,
the Telerik team