Contradiction with Matthew 13:10-11
Jesus tells his disciples that knowledge of the mysteries of the kingdom of heaven is meant for them, suggesting a preference for revealing truth to a select few, contrary to John 16:25 where he speaks of openly revealing things.
Matthew 13:10-11: And the disciples came, and said unto him, Why speakest thou unto them in parables?
Contradiction with Mark 4:33-34
Jesus communicates with the public using parables and only explains them privately to his disciples, which contradicts John 16:25's message of speaking plainly.
Mark 4:33-34: And with many such parables spake he the word unto them, as they were able to hear [it].
Contradiction with John 10:6
The figurative speech used by Jesus was not understood by the listeners, showing contrast to the implication in John 16:25 of speaking plainly to be understood.
John 10:6: This parable spake Jesus unto them: but they understood not what things they were which he spake unto them.
Contradiction with John 18:20
Jesus claims he spoke openly to the world and in secret about nothing, which opposes the notion in John 16:25 of previously speaking figuratively and later intending to speak plainly.
John 18:20: Jesus answered him, I spake openly to the world; I ever taught in the synagogue, and in the temple, whither the Jews always resort; and in secret have I said nothing.