People with AOS and people with aphasia often produce inconsistent variants of errors when they are asked to repeat challenging words several times sequentially. The finding that error consistency is similar or lower in aphasia with AOS than in aphasia without AOS is incompatible with recommendations that high error consistency be used as a diagnostic criterion for AOS. At the same time, group differences in the opposite direction are not sufficiently systematic to warrant use for differential diagnosis between aphasia with AOS and aphasia with phonemic paraphasia. Greater attention should be given to error propagation when estimating reliability of derived measurements.