Criticism of Mark

Bruce, F.F.. The New Testament Documents: Are They Reliable? (p. 47). Kingsley Books. Kindle Edition.

As appears from the textual evidence, the original ending of this Gospel may have been lost at a very early date, and the narrative breaks off short at 16:8. (The verses which follow in our Bibles are a later appendix.)

F. F. Bruce. The Canon of Scripture (Kindle Locations 1202-1206). Kindle Edition.

On Mark’s record Papias speaks somewhat defensively, as though he knew of criticisms that had been voiced against it, especially on the ground that its order was defective. To this Papias replies that Mark did not set out to write an orderly account: his aim was to record in writing whatever Peter had to tell of the works and words of Jesus; and Peter simply mentioned from time to time those things which the circumstances of the moment required. In what he wrote down Mark made no mistake: in order, as in matter, he adhered to what Peter said.

F. F. Bruce. The Canon of Scripture (Kindle Locations 2613-2614). Kindle Edition.

As for Mark, the tradition that his record is based (in part at least) on the preaching of Peter may have a foundation in fact, but no appeal is made to Peter’s authority in the course of the record.