Just to be clear, the tabs actually are working most of the time. I've implemented the tabs using rules and panels, as one would expect. Here, the default tab specifically will not display on the initial load when you go into "Edit Properties". It seems to be some sort of issue where it's looking for the last tab used, but can't find one and doesn't use the default that was set (I think). This can be solved by clicking on the other tab, which displays properly, and then clicking again on the original tab, after which there's no more problems.
My question is how can I make sure that it displays initially? Whether it be by custom JS or settings, I can't see a way to fix it.
There is one error in console that is thrown that I'm not sure if it's relevant, though since it looks to be in the nintex source might be something common that I don't know about (though I'm suspicious that it might be blocking the running of my JS).
Attached are images of what it looks like after the initial load, what it looks like after switching tabs, and the console error. I'm glad to provide other information as needed as well.
Thanks in advance.