Yes, unfortunately the border affecting PopUp position is not an easy bug to fix and it may take a while until we fix it. The problem is that jQuery's offset() and position() methods do not take account of the body border properly. Additionally the PopUp's animation container is absolutely positioned in the body, but the body is usually not its offsetParent (e.g. when its position is static) and it should be positioned relative to the documentElement, however if we set position: relative to the body, the offset() and position() return the same values as when not:
We'll try to fix it in the future, but I can't commit to an exact time frame. As a workaround you can move the border to a different element.
the Telerik team
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