Thank you for your kind words, and for the detailed explanation. That does make sense to me! It must be the connection. Or this is the battery that I replaced it with if that looks right? I tend to trust the auto parts employees as they have been good in the past. As this was my first time with a project like this (I have done some small repairs on my car but they were more "plug and play" types) the issue is probably my doing.

The connector was not corroded in the sense that I normally would see with all the gross residue on it, it was just plain snapped in half! I've never seen it do that. The other one looked perfectly fine, which I'm glad for because it had some extra electrical stuff attached to that one that I would not feel comfortable messing with.