Custom Workflow Task with custom content type not working in VS 2012

I have created custom content type inherited from Workflow Task (SharePoint 2013) as i have to remove and add fields according to use.

I also created a custom workflow task list, which uses Task(default),Summary Task,Workflow Task (SharePoint 2013)(my custom content type),Workflow Task.

I have tried to make an exact copy Workflow Tasks, then associated workflow with document library.My custom Workflow Tasks is exactly same but, differs in Workflow Task (SharePoint 2013) which causes problem.

Workflow works fine with inbuilt Workflow Tasks but not with me custom list with custom content type.

I am doing all the things in Visual Studio programmatically. I think,my custom Workflow Task (SharePoint 2013) creates problem.

Elements.xml

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://ift.tt/sQmbje">
<!-- Parent ContentType: Workflow Task (SharePoint 2013) (0x0108003365C4474CAE8C42BCE396314E88E51F) -->
  <ContentType ID="0x0108003365C4474CAE8C42BCE396314E88E51F00526BE6B656AD4301B5116F892EA5A019" Name="WorkflowCT" Group="Paperless CT Group" Description="Content Type for workflow" Inherits="TRUE" Version="0">
    <FieldRefs>
      <FieldRef ID="{E32A6287-4DE5-49F1-9133-9FD15364395B}" DisplayName="Comments" Name="WFComments" NumLines="6" ShowInEditForm="TRUE" ShowInNewForm="TRUE" ShowInDisplayForm="TRUE" />
      <FieldRef ID="{B7031F2B-19C3-4035-8FF0-775AD2160D79}" DisplayName="WF Task Outcome" Required="FALSE" Name="WFTaskOutcome" ShowInEditForm="TRUE" ShowInNewForm="TRUE" ShowInDisplayForm="TRUE" />
    </FieldRefs>
  </ContentType>
</Elements>