Open Library in Grid View, Browse mode.
Arrange column widths such that when you turn on the Info panel, the right-most visible column is partially obscured by the info panel, and the text in at least some rows in that column is truncated.
Hover the mouse over any truncated text in that right-most column.
Result: Popup showing the full text does not come up.
Expect: It should come up, as it does when the info panel is not there but the far right edge of the Library window or simply the right edge of a column's width, is the thing truncating the text.