Select two documents such that you are viewing them in scrivenings mode.
Select text in the first section.
Select text in the second.
The text in the first will remain highlighted. I you press Ctrl-C, only the text in the second will be copied.
When Scrivenings gets updated so that the text works more like a contiguous document, with one selection point (that can span between sections as though there is no separation), then this problem will be indirectly resolved. 