This is the thing that bugged me the most as well. In fact, it was the only thing that detracted from what was otherwise a very pleasant experience.
I don't know if Barnes was just running with the "If you don't know what's bothering me, I'm not going to tell you" thing that gets pinned on women sometimes, but the last bit of the book made me feel like I was watching LOST in space (see this trope).
In fact, the "I know the answer but won't tell you" trope is one of my pet peeves. It seems like such a lazy way to build drama.
Other than this, a rather enjoyable book. I'll admit that at the end I went and looked for other people's responses due to the overwhelming sense of "wait, what just happened!?!"