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 (!crypter.SetKeyFromPassphrase(strWalletPassphrase, kMasterKey.vchSalt, kMasterKey.nDeriveIterations, kMasterKey.nDerivationMethod))
        return false;
    if (!crypter.Encrypt(vMasterKey, kMasterKey.vchCryptedKey))
        return false;
    {
        LOCK(cs_wallet);
        mapMasterKeys[++nMasterKeyMaxID] = kMasterKey;
        if (fFileBacked)
        {
            assert(!pwalletdbEncryption);
            pwalletdbEncryption = new CWalletDB(strWalletFile);
            if (!pwalletdbEncryption->TxnBegin()) {
                delete pwalletdbEncryption;
                pwalletdbEncryption = NULL;
                return false;
            }
            pwalletdbEncryption->WriteMasterKey(nMasterKeyMaxID, kMasterKey);
        }
        if (!EncryptKeys(vMasterKey))
        {
            if (fFileBacked) {
                pwalletdbEncryption->TxnAbort();
                delete pwalletdbEncryption;
            }
            
            
            assert(false);
        }
        
        SetMinVersion(FEATURE_WALLETCRYPT, pwalletdbEncryption, true);