Yeah, it might be too unlikely for the tank failure to be the next flight. I only wonder about it because of the "double whammy" effect. (I was presuming something like an abort explosion: not directly related to design, but an issue of, say, bad landing site choice--anything that doesn't uncover the tank problem.)
I think that's definitely the most likely failure possibility.
The landing was easily the highest risk part of the mission. The LM was down to fumes when it landed, and an abort that close to the surface had a high risk of turning fatal.
Other near mechanical problems we saw on the LM on other missions - landing radar failure, accidental abort discrete switch set, LM computer overload, etc. - could have killed the landing, but were less likely to kill or strand the crew. The ascent engine was simple and very reliable - the real problem there might be the rendezvous with the CSM in lunar orbit.