wow, this looks odd,
however this can happen if you have an "armor type" block on top.
As it does use "blast-protection" mechanics now, and calculates like a shadow behind the block and keeps those blocks intact.
But that exact shape is very odd, unless there were 2-3 blocks with unusual high block HP.
If you can sort of reproduce that, may you give us a blueprint of the combination that causes this?
(Yes, I was working and did not see this thread yet. =) As my holidaytime is now over, my reaction times should slightly increase.)
- Andy