Currently, due to the specificity of the internal implementation for this scrolling behavior, the possible solution that I can suggest is to hide the row header by setting the ShowRowHeaderColumn property to false.
this.radGridView1.ShowRowHeaderColumn = false;
I would like to follow up with an additional case where the vertical scrollbar is stuck if the multiple selection starts from a pinned column. Please have a look at the attached gif file for better illustration.
This case should be covered as well when addressing this item.
Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik
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