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.

{
            if (pwallet->mapAddressBook.count(r.destination))
            {
                map<CTxDestination, CAddressBookData>::const_iterator mi = pwallet->mapAddressBook.find(r.destination);
                if (mi != pwallet->mapAddressBook.end() && (*mi).second.name == strAccount)
                    nReceived += r.amount;
            }
            else if (strAccount.empty())
            {
                nReceived += r.amount;
            }
        }
    }
}
/**
 * Scan the block chain (starting in pindexStart) for transactions
 * from or to us. If fUpdate is true, found transactions that already
 * exist in the wallet will be updated.
 */
int CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate)