Probably what you are thinking of is the question of whether the red shift observed in astronomical objects is due to motion of the objects away from us or some other cause, and whether one can reliably say that a quasar with a red shift X is really a distance Y away, as calculated from hypothesis regarding the origin of the cosmological red shift, and whether one can reliably infer that the universe is expanding at such and such a rate, is such and such an age, etc. On this it is fair to say there is considerable consensus, but some room for challenge.