I heard a year or so ago from an LFS owner, when I was looking into getting a JBJ nano, that they had several customers with JBJ 24 gallon Nano Cubes crack. I hadn't heard about any 12's cracking. From what he said JBJ claimed they were fixing the problem. I have read of a couple cracking on RC since then. Not sure if they were the old ones or not.
FWIW, Chris