This box got an in-service inspection somewhere five months ago, and had a CSC updated.
It is believed that the corner casting bottom aperture has been worn-out then, apparently the client ignored such worn-out damage to put it for use continuously. From stage 1 photo, just half percentage thickness remains after worn-out. Then, it could cause stress cracking due to remaining wall thickness collapsed as shown in stage 2 photo. Finally, whole material would be gone (stage 3) and an impact-like breakage/breach happens. It is extremely dangerous condition during the transportation.