Contradiction with Exodus 16:14
It describes manna as "a small round thing, as small as the hoar frost on the ground," differing in detail from the color and appearance described in Numbers 11:7.
Exodus 16:14: And when the dew that lay was gone up, behold, upon the face of the wilderness [there lay] a small round thing, [as] small as the hoar frost on the ground.
Contradiction with Exodus 16:31
It describes the taste of manna as "wafers made with honey," while Numbers 11:8 elsewhere describes it as tasting like "oil," showing a contradiction in taste description.
Exodus 16:31: And the house of Israel called the name thereof Manna: and it [was] like coriander seed, white; and the taste of it [was] like wafers [made] with honey.