When Dr Krippendorf is reading a fax at the beginning of the movie, the fax is dated April 1. It says that everyone is looking forward to his lecture the next Monday evening at 8PM. Then, a few scenes later (on the same morning) Dr Krippendorf passes a handbills pinned to a bulletin board on his college campus stating that his lecture will be on April 13th from 6-7 PM. It's not possible for his lecture to go from the first week in April to the middle of April on the same morning.
Krippendorf repeatedly refers to the Shelmikedmu as a Neolithic tribe, but their level of development would mean they are technically Paleolithic (pre-Neolithic).