Spam score

The reducing traffic must be due to some other factors and not due to spam score. It must be investigated.

While it is a positive thing to have low spam score, it has nothing to do (directly) with your ranking positions. So I wouldn't be looking for a relationship there. Also, spam score is just a third party metric developed to mimic how search engines evaluate those things. The thing is, it has nothing to do with the real algorithm so it's yet another potentially helpful artificial number but you can't use non-google metric like spam score with google metric (ranking position) in the same formula.