Because of the depth of the memorial in hubbing process, usually first in series of hubs(center out?) and proximity to edge, then throw in die metal flows outwards causing a stretching of devices as they approach closer to the rim is the reasons cracks appear here on the corners most often. Also why so many "spiked/cracked heads" or lightning strikes on Monticello's dome, or letter/number devices near rim, or...
"...and the beat goes on..."
