Contradiction with Matthew 15:6
Jesus criticizes the Pharisees for holding traditions over God's commandments, which contradicts the emphasis on traditions in 2 Thessalonians 2:15.
Matthew 15:6: And honour not his father or his mother, [he shall be free]. Thus have ye made the commandment of God of none effect by your tradition.
Contradiction with Mark 7:8
Jesus rebukes putting traditions above God's commands, contrasting with upholding traditions of the apostles in 2 Thessalonians 2:15.
Mark 7:8: For laying aside the commandment of God, ye hold the tradition of men, [as] the washing of pots and cups: and many other such like things ye do.
Contradiction with Colossians 2:8
Warns against being taken captive by tradition, which may contradict holding firmly to traditions in 2 Thessalonians 2:15.
Colossians 2:8: Beware lest any man spoil you through philosophy and vain deceit, after the tradition of men, after the rudiments of the world, and not after Christ. [rudiments: or, elements] [make a prey: or, seduce you, or, lead you astray]
Contradiction with Galatians 1:14
Paul talks about his former life in Judaism and excelling in traditions, which he left, in contrast to the directive in 2 Thessalonians 2:15.
Galatians 1:14: And profited in the Jews' religion above many my equals in mine own nation, being more exceedingly zealous of the traditions of my fathers. [equals: Gr. equals in years]
Contradiction with 1 Peter 1:18
Refers to traditional ways as something believers were redeemed from, which can be seen in opposition to upholding tradition as in 2 Thessalonians 2:15.
1 Peter 1:18: Forasmuch as ye know that ye were not redeemed with corruptible things, [as] silver and gold, from your vain conversation [received] by tradition from your fathers;