When Barnabas, Julia, and Stokes return to 1971, all is calm and Liz acts as if they've never been away. How can that be when the last time they were all in the present was the summer/fall of 1970, and months had passed since then (during which they were in 1840, and absent from present time)?
Unlike Vicki's trip to the past and return to the present during which present time was suspended, time continued to progress normally in 1970 and 1971. Accordingly, Barnabas and Julia's absence should have been conspicuous, and their sudden return equally conspicious; and Liz should not in all logic have behaved as if everything were normal and uneventful.
Also, of course, there is the unexplained absence of Barnabas' I-ching entranced body in the present. How could he have returned from the past in a different way than when he went there? Could it be that his I-ching entranced body suddenly disappeared when he, Julia, and Stokes traversed the Stairway Through Time back into the present?