A first major contradiction lies in the closing of the covenant occurring in the temple before the temple has been purified. To this is added that throughout 2 Kgs 23:4-20 nothing is said of the law book. This shows that 23:1-3, 21-23 and 23:4-20 did not originally belong together. That Hilkiah and the guards appear (only!) in v. 4aα which forges a link with 2 Kgs 22 (and 23:24 for Hilkiah) is no objection to our hypothesis since Hilkiah and the guards play no further role in 23:4-20. They serve merely as transition figures.
This is a connection to a second broad contradiction long known to exegesis: it is impossible that all these cult reforms took place at the start of the 18th year of the king’s rule (cf. 2 Kgs 22:3) and that the Passover feast also took place in that same 18th year (cf. 2 Kgs 23:23) for this leaves an interval of but two weeks between New Year (1 Abib) and the Passover feast (15 Abib). N. Lohfink offered a good interpretation of this: 2 Kgs 22:3 and 23:23 are the starting and finishing borders of the ‘Auffindungsgeschichte’. Both verses contain the name Josiah with his title (מלך יאשׁיהו) and the date. The author of 2 Kgs 22-23:3, 21-23 uses these verses as inclusion to delimit his passage. This does not remove the tension, but indicates a redactional laying in the text which can only be explained via redaction criticism. (Erik Eynikel, The Reform of King Josiah and the Composition of the Deuteronomistic History [Leiden: E.J. Brill, 1996], 320-21)