Contradiction with Isaiah 38:5
Isaiah 38:22 is about Hezekiah asking for a sign to go up to the house of the LORD, while Isaiah 38:5 shows the LORD already promising Hezekiah 15 more years of life, indicating that Hezekiah received reassurance without needing additional signs.
Isaiah 38:5: Go, and say to Hezekiah, Thus saith the LORD, the God of David thy father, I have heard thy prayer, I have seen thy tears: behold, I will add unto thy days fifteen years.