Is resitting AS a a sign?

I'm a y12 student currently sitting CIE AS exams in New Zealand, I'm hoping to do medicine and I do the 3 Sciences along with Maths and English.

The Chemistry long answer paper was an utter disaster for me (e.g suggesting that BrCl was a liquid despite knowing that Br2 is a gas at RTP), and the bio practical as well to an extent, I'm not bad at the sciences I just had really bad luck and I panicked during those particular exams. (I got high As for Chem/Bio in my mocks my marks were among the top ten of the students sitting it at my school) I know I'm capable of achieving an A.

So I'm looking at a B for Chem right now (Bio not so much since the the practical only accounts for around 20%), I know you have to get AAA to be competitive in medicine so I'm planning to resit the AS Chem exam next year in June if I get anything but an A which is looking quite likely.

I'm currently aiming for the University of Auckland and Otago and as far as I know, they don't care about resits, as long as you meet the grades you can get a place in HSFY (the prerequisite to Medicine/Dentistry etc...) which are apparently AAB.

But does resitting reflect poorly on myself? Does having to resit an AS exam mean I won't be able to cope in the incredibly competitive HSFY? I know that universities expect med students to perform well at all times and with the first go but that exam was unlike past papers I looked at and I was simply caught off guard.