Outside stock basis is not necessarily identical to the sum of the equity accounts. You don't reconcile outside basis to the balance sheet. 

Time to set up an Excel reconciliation and go back to a known starting point, then work forward from there. I put a note in my corporate workpapers that lets me know when and why the equity / outside basis difference arose, and the amount of it, because otherwise I'll have to do that same reconciliation in some future year.