Loss of LH2 during transport

During the transit of 10 000 gallons (ca. 39000 l) LH2 transport vessel, the venting rate became extremely high . The annular vacuum appeared to be lost showing large patches of condensed water at the lower half of the outer vessel shell. It was necessary to stop many times to manually vent. In addition, a number of times the safety valve with an opening pressure of 55 psig (ca. 3.8 bar) was relieved. The tanker had only 3000 gallons (ca. 11400 l) remaining which was transferred to the storage tank. Crack was found in the lowest portion of the carbon steel jacket.
[Ordin, NASA (1974)]

INITIATING CAUSE
The outer jacket of the cryo-vessel cracked due to the presence of solid first, then liquid air at the bottom of the outer jacket. Air entered vacuum space during to cryo-pumping of liquid hydrogen. This air remained as a solid until the liquid hydrogen transfer was completed, after which, it melted. The crack was most likely caused by the thawing of solid air.
ROOT CAUSE or CONTRIBUTING CAUSE
The report does not provide any explanation why the vacuum failed during transport. Did the jacked crack during the journey? For which reason? Is this a design shortcoming?

Out jacket of the vacum insulation

A loss of approximatly 1800 kg of hydrogen (Assuming a cost of hydrogen of 12 to 15 US$, an order of magnitude of the propoerty total loss could be estimated)