UI selection with materials overlay is wrong

If I select a view in the materials overlay when there is a stack of items on a tile, items which are featured in the overlay are rendered at the front of the stack.  When I click on the item, I expect this item to select.  If the item is not actually at the top of the stack, something else will be selected.

Usally in ONI if items are rendered on top of each other, the item that I actually click on is the one that's selected with the first click.  This is not respecting the materials overlay.  Lead appears in the tooltip, but clicking on the lead selected obsidian

This is because obsidian was the first item under the mouse without the overlay.