I think it is not rare for errors in citing to be repeated because no-one bothers to go back to the original source.

Not reading the paper at all can be dangerous. I once read a paper in which the authors had unwittingly rediscovered, but in inferior form, mathematical results that were already proved in one of the papers they cited. Fortunately for the authors, I was refereeing their paper, and had read the paper they cited, so I was able to save them the embarrassment of publication.