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 walletdb(strWalletFile);
    if (!walletdb.TxnBegin())
        return false;
    int64_t nNow = GetAdjustedTime();
    
    CAccountingEntry debit;
    debit.nOrderPos = IncOrderPosNext(&walletdb);
    debit.strAccount = strFrom;
    debit.nCreditDebit = -nAmount;
    debit.nTime = nNow;
    debit.strOtherAccount = strTo;
    debit.strComment = strComment;
    AddAccountingEntry(debit, &walletdb);
    
    CAccountingEntry credit;
    credit.nOrderPos = IncOrderPosNext(&walletdb);
    credit.strAccount = strTo;
    credit.nCreditDebit = nAmount;
    credit.nTime = nNow;
    credit.strOtherAccount = strFrom;
    credit.strComment = strComment;
    AddAccountingEntry(credit, &walletdb);
    if (!walletdb.TxnCommit())
        return false;
    return true;
}
bool CWallet::GetAccountPubkey(CPubKey &pubKey, std::string strAccount, bool bForceNew)