We have not been able to run the report designer, due to missing classes, but looking at your screenshot we notice that you are using win reportviewer and not the web reportviewer as you have specified in the forum information.
This can occur in win reportviewer when you have two overlapping textboxes (see attached screenshots). Note the caution box and warning message and how these textboxes look in runtime. Basically when they are overlapping, the cangrow mechanism that would normally shift everything further down when the upper item is growing would not work. So to avoid such problems, make sure you do not have overlapping report items.
the Telerik team