Difficult to select items in lower floors when stockpile on floor above

The Young Boars.Save 99.octsav.gz

I have a stockpile on floor three with clothes lying on the ground. It's very difficult to select these items, taking multiple clicks to register. This wasn't the case previously when the same stockpile (and items) were on the ground floor with no items above. Maybe the floors below/above are interfering with the ability to select things? We have a smaller stockpile two floors below but above this clothes stockpile we also have a cotton/leather stockpile (objects here get selected properly).

Have attached the save so you can check it.

edit: it does indeed seem like the items in the stockpile in the floor above are being selected even when they're not visible. A work around is to view the floor from a side angle so the click doesn't hit the items above.

edit2: this seems to affect anything below those floors to a certain degree, for example bed chambers a few floors underground are harder to select because of items on floors above.