We are seeing issues bridging Twilio calls between the customer and agent with IVR, whisper, wait music, and call recording.

Scenario:
We have clients calling in. They enter an id to the Twilio based IVR. We play wait music. We call the agent. When the agent picks up the phone, we play the whisper of the ID. We give the agent the opportunity to look up the number. We then bridge the call and launch call recording.
Issue:
In certain situations, we lose the inbound call. We’re not entirely sure why. We don’t see any errors.
Call Flow:
1. Calls the Agent. Enqueue’s the current customer call.
File: CallAgentService.java

    public Verb callAgent(ServletRequest req, Category twilioSettings, JSONObject member) throws Exception {
        String numberCalled = getNumberCalled(req, member);
        String callSid = req.getParameter(Constants.TWILIO_PARAM_CALLSID);
        CallStatus status = callStatusRepository.findByCode(Constants.CALL_STATUS_KNOWN_ID);
        String digits = req.getParameter(Constants.TWILIO_PARAM_DIGITS);
        if(StringUtils.isNotBlank(digits)) {
            TwilioConfigUtils.saveCallStat(callLogStatRepository, callSid, status, digits);
        } else {
            TwilioConfigUtils.saveCallStat(callLogStatRepository, callSid, status);
        }
        CallLog callLog = callLogRepository.findOne(callSid);
        saveCallLog(callLog, member);
        Enqueue enqueue = new Enqueue(callSid);
        enqueue.setWaitUrl(Constants.ENQUEUE_WAIT_URL);
        enqueue.setWaitUrlMethod(HttpMethod.GET.toString());
        Call call = TwilioConfigUtils.callAgent(numberCalled, twilioSettings, env);
        if (call != null) {
            TwilioConfigUtils.saveNewCall(call, callLog, callLogRepository);
            status = callStatusRepository.findByCode(Constants.CALL_STATUS_AGENT_START);
            TwilioConfigUtils.saveCallStat(callLogStatRepository, callSid, status);
            return enqueue;
        } else {
            Say sayError = new Say("We are sorry an error has occurred.");
            sayError.setLanguage(Constants.SPOKEN_LANGUAGE);
            return sayError;
        }
    }

2. Creates the outbound call to the agent with the whisper.
File: TwilioConfigUtils.java

    public static Call callAgent(String called, Category twilioSettings, Environment env) {
        log.debug("Calling agent");
        try {
            String acctSid = getTwilioConfigByCode(twilioSettings, Constants.TWILIO_ACCOUNT_SID);
            String authToken = getTwilioConfigByCode(twilioSettings, Constants.TWILIO_AUTH_TOKEN);
            String phoneNumber = getTwilioConfigByCode(twilioSettings, Constants.TWILIO_AGENT_PHONE);
            TwilioRestClient client = new TwilioRestClient(acctSid, authToken);
            // Build a filter for the CallList
            List params = new ArrayList<>();
            String localhost = env.getProperty("rest.main.url");
            params.add(new BasicNameValuePair("Url", localhost + Constants.WHISPER_AGENT));
            params.add(new BasicNameValuePair("To", phoneNumber));
            params.add(new BasicNameValuePair("From", called));
            params.add(new BasicNameValuePair("Method", HttpMethod.GET.toString()));
            params.add(new BasicNameValuePair("Record", Boolean.TRUE.toString()));
            params.add(new BasicNameValuePair("StatusCallback", localhost + Constants.AUDIO_RECORD_CALLBACK));
            params.add(new BasicNameValuePair("StatusCallbackMethod", HttpMethod.GET.toString()));
            CallFactory callFactory = client.getAccount().getCallFactory();
            Call call = callFactory.create(params);
            return call;
        } catch (Exception e) {
            log.error(e);
        } finally {
            log.debug("Agent called");
        }
        return null;
    }

Agent Call on Twilio Logs

3. Whispers to the Agent
File: WhisperAgentServlet.java

 @Override
    public void service(ServletRequest req, ServletResponse response) throws ServletException, IOException {
        log.debug("Entering WhisperAgentServlet");
        String callSid = req.getParameter(Constants.TWILIO_PARAM_CALLSID);
        CallLog callLog = callLogRepository.findOne(callSid);
        CallStatus status = callStatusRepository.findByCode(Constants.CALL_STATUS_AGENT_CONNECT);
        TwilioConfigUtils.saveCallStat(callLogStatRepository, callLog.getParentCallSid(), status);
        TwiMLResponse twiml = new TwiMLResponse();
        Long clientId = callLog.getClientId();
        try {
            if (callLog == null) {
                log.debug(twiml.toXML());
                response.setContentType(Constants.CONTENT_TYPE_XML);
                response.getWriter().print(twiml.toXML());
                return;
            }
            Category twilioSettings = categoryRepository.findCategoryByCodeAndClientId(Constants.TWILIO_SETTINGS, clientId);
            String msg;
            if (StringUtils.isNotBlank(callLog.getMemberName()) && StringUtils.isNotBlank(callLog.getMemberLastName())) {
                msg = TwilioConfigUtils.getTwilioConfigByCode(twilioSettings, Constants.TWILIO_WHISPER_AGENT_MENU_MEMBER_INFO);
                Map<String, String> map = new HashMap<>();
                map.put(Constants.TWILIO_MSG_VAR_FIRSTNAME, callLog.getMemberName());
                map.put(Constants.TWILIO_MSG_VAR_LASTNAME, callLog.getMemberLastName());
                String memberId = callLog.getCsMemberId();
                if (StringUtils.isBlank(memberId)) {
                    memberId = callLog.getClientMemberId();
                } else {
                    memberId = "1111" + StringUtils.leftPad(memberId, 8, '0');
                }
                StringBuilder sbMemberId = new StringBuilder();
                for (char c : memberId.toCharArray()) {
                    sbMemberId.append(c).append(", ");
                }
                map.put(Constants.TWILIO_MSG_VAR_MEMBER_ID, sbMemberId.toString().trim());
                msg = StrSubstitutor.replace(msg, map);
            } else {
                msg = TwilioConfigUtils.getTwilioConfigByCode(twilioSettings, Constants.TWILIO_WHISPER_AGENT_MENU_NO_MEMBER_INFO);
            }
            Say incomingCall = new Say(msg);
            incomingCall.setLanguage(Constants.SPOKEN_LANGUAGE);
            Dial dial = new Dial();
            Queue queue = new Queue(callLog.getParentCallSid());
            dial.append(queue);
            twiml.append(incomingCall);
            twiml.append(dial);
        } catch (TwiMLException e) {
            log.error(e);
            Say error = new Say("We are sorry an error has occurred while connecting.");
            error.setLanguage(Constants.SPOKEN_LANGUAGE);
            try {
                twiml = new TwiMLResponse();
                twiml.append(error);
            } catch (TwiMLException e1) {
                log.error(e1);
            }
            callLog = callLogRepository.findOne(callLog.getParentCallSid());
            Category twilioSettings = categoryRepository.findCategoryByCodeAndClientId(Constants.TWILIO_SETTINGS, clientId);
            TwilioConfigUtils.releaseQueueWithError(callLog, twilioSettings, env);
        }
        log.debug(twiml.toXML());
        response.setContentType(Constants.CONTENT_TYPE_XML);
        response.getWriter().print(twiml.toXML());
    }

Customer Call on Twilio Logs
Where does the Hangup event come from? When we do our tests we are still on the call?!??!