Furthermore, each time a solid and consistent evolutionary explanation for an adaptation is found, this is in turn evidence for the background theory of evolution as a whole, for it is the sort of evidence you are likely to find when evolution is true and unlikely to find if evolution is false; and every time an adaptation is found that stubbornly resists any explanations as to how it can be sustained, this is evidence AGAINST evolution, for the converse reason.
If, over time, we collect literally millions of solid, well-understood, and predictive explanations of how particular features of organisms are generated by the landscape of evolution, this quickly forms a HUGE mountain of evidence in evolution's favor. If there are a handful of cases of adaptations that seem to defy all explanations -- of which I don't know any, but which surely exist -- then this can mean two things: either it means that evolution as we understand it is wrong, or it means that we haven't thought of the explanation YET but it exists anyway.
The size of the two mountains involved are what determines the overall estimate as to which of these two possibilities is most likely. The larger the mountain of evidence in the form of confirmed evolutionary explanations of behaviors, the more likely that we simply didn't think of the right answers for the open questions yet; the larger the collection of open questions, the more likely that there isn't a right answer and evolution is simply wrong.
At that point, it has become a numbers game. The critical numbers here are "literally millions and millions" versus "a couple of handfuls". You would have to talk to a scholar of evolutionary biology (which I am definitely not) for a better estimate of the two sizes of mountain, but a case or two that are real stumpers prove nothing. And an offered case or two that in fact we understand perfectly well, proves the opposite.