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 (fFileBacked)
        {
            if (!pwalletdbEncryption->TxnCommit()) {
                delete pwalletdbEncryption;
                
                
                assert(false);
            }
            delete pwalletdbEncryption;
            pwalletdbEncryption = NULL;
        }
        Lock();
        Unlock(strWalletPassphrase);
        
        if (IsHDEnabled()) {
            CKey key;
            CPubKey masterPubKey = GenerateNewHDMasterKey();
            if (!SetHDMasterKey(masterPubKey))
                return false;
        }
        NewKeyPool();
        Lock();
        
        
        CDB::Rewrite(strWalletFile);
    }
    NotifyStatusChanged(this);
    return true;
}
DBErrors CWallet::ReorderTransactions()