Can we really trust the literature?
Let me point out here that "can a paper be trusted" and "all of the calculations in the paper are exactly correct" are not necessarily related. This is something that people get wrong about research, and in particular single papers, all the time. Academic papers are useful dialogue. They are not necessarily 100% accurate or unimpeachable.
Peer review is designed to catch methodological errors. It confirms that the authors followed sound scientific principles as appropriate to their field. Most peer review does not check for errors in calculation, and typically could not even if they wanted because the peer reviewer does not have access to all of the paper's data. However, peer review does confirm that a group of experts all read the paper and agreed that the methods and conclusion make sense.
A paper published in a good venue is not strong because it is guaranteed to be 100% accurate, it's strong because the expert community of reviewers thinks it is accurate. I would assume, though I can't cite any evidence, that academic papers at good venues have a much lower error rate than similar documents that do not go through a rigorous vetting process.
As to whether this error should be reported- it really depends. If this is a purely theoretical result, if it is empirically in doubt, if it substantially changes the result of the paper, then the error should really likely be reported. If the calculation is wrong but the intuition and the model are solid, and there is strong empirical evidence for the model, then the calculation error probably isn't that meaningful.
Here's a practical yardstick: if reporting the error substantially advances the scientific conversation, then it is a publishable result that should be published, just like any other publishable result. If reporting the error is just fixing errata and not substantially contributing to the body of knowledge, then it's not publishable and probably nobody cares.