First, I want to say this bug is still around and is strange.
Other posts on this are here:
here and here here
In this image, you can see that the interior of the wall (and the solid base) is filled when the clippingplane intersects with one of the block objects, but not the other (the highlighted one).
Second, this bug has been previously difficult to recreate.
Since these two objects are mirrors of each other, it’ got me thinking if this has to do with the math being done based on the zero point.
It turns out that if I edit the block and move the base point around, it gets the clipping plane and the fill to behave in different ways, occasionally even cooperating as desired.
This leads me to believe that there’s something about the fill occurring in +x,+y space but the block drawing the object in it’s own +x,-y space that cancels each other out.
If there’s enough interest and this problem is common enough to need it, I can make a better set of images to illustrate what I’ve found.