When a pass of CreateTransaction fails to select enough bitcoin to meet the nFeeNeeded the next pass through may select a far smaller collection of inputs.  Currently it will continue to use the old fee amount based on the larger set of inputs, which can cause a non-trivial over-payment.

This may be the cause of the behavior reported here: https://www.reddit.com/r/Bitcoin/comments/5ltw5n/bitcoin_core_v0131_sends_enormously_high_fee/

Long ago fixing this was tricky due to a catch-22 between signing the transaction and knowing how much fee was required.  But after #9465 the whole algorithm will run using a dummy signature, so when there is already a change output fixing up the fee after finding a sufficient transaction should be a matter of a ~2 line change.

{
                CWalletDB(strWalletFile).EraseDestData(strAddress, item.first);
            }
        }
        mapAddressBook.erase(address);
    }
    NotifyAddressBookChanged(this, address, "", ::IsMine(*this, address) != ISMINE_NO, "", CT_DELETED);
    if (!fFileBacked)
        return false;
    CWalletDB(strWalletFile).ErasePurpose(CBitcoinAddress(address).ToString());
    return CWalletDB(strWalletFile).EraseName(CBitcoinAddress(address).ToString());
}
bool CWallet::SetDefaultKey(const CPubKey &vchPubKey)
{
    if (fFileBacked)
    {
        if (!CWalletDB(strWalletFile).WriteDefaultKey(vchPubKey))
            return false;
    }
    vchDefaultKey = vchPubKey;
    return true;
}
/**
 * Mark old keypool keys as used,
 * and generate all new keys 
 */
bool CWallet::NewKeyPool()