In the environment window, stacked items of a similar type, (for example a stack of 4 rags), will show a count of zero in the lower corner while the object is in the left environment window.
If the item is dragged to the personal (right window) inventory pane, the item correctly shows the number in the stack. {F31958} {F31959}
From what I've seen, it's not any particular type of item, as long as it stacks. Also, being on "the ground" does not reproduce the issue. The affected items must be in a container, on the ground.
This also appears to affect some item's with percentages instead of just integer counts. I the two screenshots I'm attaching, You'll notice the canned goods the cans in the fireplace show 0%. In the second screenshot, I've moved the can of peaches from the fireplace to position 4x5 (x by y) in my drybag, which then correctly shows 97% remaining.
Other items in the fireplace like shotgun shells and pile of guts do not appear to be affected.