It looks like it was a mistake in the testing procedure and not a design problem. The upper tank was being filled while the tank below appears to be empty (as there was no frost covering the lower tank to indicate that it was also pressurized with liquid nitrogen. Also, I don't think the lower tank was filled with water, as it would have gushed out when the lower tank crumpled). I think this was an unintentional mistake. I can't imagine they expected an empty tank, even a steel one, could hold up when thousands of tons of liquid nitrogen filled the tank above. It appears that somebody was not thinking clearly when they designed the test.
This being the case, I don't see this slowing down SN4. Although I can certainly imagine someone losing their job over this.
Maybe the vehicle that gets you into space and the vehicle that you use while in space should not be the same vehicle. Would it be easier to build something that can leave and return to earth and something different that will always remain in space? One design to deal with gravity and atmosphere, and one design to deal with a vacuum and radiation.