I think a good explanation for all the discrepancies found in the Chronicles, is that perhaps these stories were all oral histories in Narnia before they were eventually put into written form (remember in TSC when Jill and Eustace listened to someone tell 'The Horse and His Boy'?) and therefore are prone to the mistakes made when a story is repeated, and repeated, from story teller, to listener, to the next, etc. (ever played 'telephone'?)
I think that Lewis was scholar enough to never forget that his own Christian bible was this sort of text...(and therefore full of contradictions and mistakes)...
And BTW, if you read the CoN in the original order, these discrepancies are much less obvious...
*I would just like to note, that my dearest Coracle (who I love) is making a statement of BELIEF in the following post, not FACT--which is just fine by me, but should be recognized as such.
Hugs dear Coracle--hugs to you