User Task Not Found Exception using BDM in Bonita ui

I have developed test application using BDM and Bonita ui designer in Bonita BPM Community Edition Version : 7.3.1. I have business object named "BusinessObject1" with one string type name and "namebd" as Business Variables of "BusinessObject1".
In Step1 i created one Input:

formInput | {"nameInput" : {"name" : ""}} | JSON
in step1 operations i added:
namebd steName nameInput.name

In step2 i created one input :
taskId id URL parameter
task ../API/bpm/userTask/{{taskId}} External API
context ../API/bpm/userTask/{{taskId}}/context External API
namebd ../{{context.namebd_ref.link}} External API

Error Log:
2016-12-04 09:43:12.531 -0800 WARNING: org.restlet.Component.BonitaRestletApplication Exception or error caught in server resource
org.bonitasoft.engine.bpm.flownode.UserTaskNotFoundException: USERNAME=walter.bates | Activity instance with id 7675984443287227753 not found
at org.bonitasoft.engine.api.impl.ProcessAPIImpl.getUserTaskContract(ProcessAPIImpl.java:5678)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.bonitasoft.engine.api.impl.ServerAPIImpl.invokeAPI(ServerAPIImpl.java:462)
at org.bonitasoft.engine.api.impl.ServerAPIImpl$2.call(ServerAPIImpl.java:431)
at org.bonitasoft.engine.transaction.JTATransactionServiceImpl.executeInTransaction(JTATransactionServiceImpl.java:312)

2016-12-04 10:44:46.291 -0800 SEVERE: org.bonitasoft.web.rest.server.api.resource.CommonResource org.bonitasoft.engine.bpm.data.DataNotFoundException: USERNAME=walter.bates | org.bonitasoft.engine.core.process.instance.api.exceptions.SFlowNodeNotFoundException: Flow node instance with id 4002 not found
org.bonitasoft.web.toolkit.client.common.exception.api.APIException: org.bonitasoft.engine.bpm.data.DataNotFoundException: USERNAME=walter.bates | org.bonitasoft.engine.core.process.instance.api.exceptions.SFlowNodeNotFoundException: Flow node instance with id 4002 not found
at org.bonitasoft.web.rest.server.api.bpm.flownode.ActivityVariableResource.getTaskVariable(ActivityVariableResource.java:28)

Caused by: org.bonitasoft.engine.bpm.data.DataNotFoundException: USERNAME=walter.bates | org.bonitasoft.engine.core.process.instance.api.exceptions.SFlowNodeNotFoundException: Flow node instance with id 4002 not found