This is 2 Kings 16:20:
And this is 2 Chronicles 28:27:
(Note for the perplexed: "slept with his fathers" is used many times in the Bible and seems to mean simply "he died".)
So, where was Ahaz buried? The first verse says "with his fathers in the city of David", and the second verse agrees, though with the caveat that he was not actually put in the same tomb. But the first verse didn't say he was. A fairly natural way of reading the first verse is:
The contradiction is more severe if you take the phrase "with his fathers" to mean close proximity, rather than just "with them in the city". I suppose it therefore borders on Minor.
By the way, there is an absolutely identical problem with the burial of Joash in 2 Kings 12:20-21 versus 2 Chronicles 24:24-25.