Yeah, the logic appears to work approximately 25% of the time, and appears to be related to the fact that there is another red box directly on top of the right side box.
If you remove the box on top of the right side redbox, everything works properly. If you add a box directly on top of the left-side box, neither works (outside of the approx. 25% [seemingly random success rate]. Finally, if you place a redbox above, instead of on top of, both of the lower red boxes, everything works as it should.
Just expanding upon the findings, so far as I can tell it is indeed a bug (using r95).
Also, why do the redboxes, upon destroying the blue boxes, move to the right? This may be another bug, perhaps.