Contradiction with Daniel 1:17
This verse states that Daniel and his friends were given knowledge and skill in all learning and wisdom, and Daniel had understanding in all visions and dreams, which contrasts with Daniel 5:15 where the king's wise men could not interpret the writing.
Daniel 1:17: As for these four children, God gave them knowledge and skill in all learning and wisdom: and Daniel had understanding in all visions and dreams. [Daniel...: or, he made Daniel understand]
Contradiction with Daniel 2:47
The king acknowledges the God of Daniel as a god of gods and a revealer of secrets, which contradicts the inability of the wise men to interpret messages from the divine as mentioned in Daniel 5:15.
Daniel 2:47: The king answered unto Daniel, and said, Of a truth [it is], that your God [is] a God of gods, and a Lord of kings, and a revealer of secrets, seeing thou couldest reveal this secret.
Contradiction with Daniel 4:18
Here, King Nebuchadnezzar calls upon Daniel specifically, knowing he can interpret dreams, which contrasts the failure of the Babylonian wise men to interpret the writing in Daniel 5:15.
Daniel 4:18: This dream I king Nebuchadnezzar have seen. Now thou, O Belteshazzar, declare the interpretation thereof, forasmuch as all the wise [men] of my kingdom are not able to make known unto me the interpretation: but thou [art] able; for the spirit of the holy gods [is] in thee.