[Eurytus]

I would think that any contradictions that are in the Hobbit are there for the simple reason that the Hobbit was originally written primarily as a children’s story and any connections to the larger mythology that Tolkien had already been working on were largely either subconscious or throwaway one liners to Gondolin and the like.

Tolkien did in fact rewrite part of the Hobbit once he worked on LOTR to enable it to tie into the latter work (the Riddles in the Dark section). But it would have been impossible to make the two works completely tie up without major rewrites.

And some of the text it contains does lead to curious conundrums that are not addressed. For example if Trolls turn to stone in the sunlight then how on earth could Melkor have hoped to use them as troops? Unless the battle was over in a single day then how could they have been used in the battle in which Hurin slew seventy of them?