We hope. The recent litterbox misses seem to have been Emily's not-too-subtle way of telling us that she really doesn't like covered litterboxes. We took the covers off, and the problem went away. Of course, with four boxes in the house you would think she could find a suitable one, but who am I to argue with Her Emilyness.
The boxes were covered in the first place because of overspray by the boys. That problem seems (we hope) to have been taken care of by moving the box away from vertical surfaces. Thereby tripling the amount of lost floor space, but never mind.