2013 Workflow BreakRoleInheritance is not applying(working) properly

• I have created workflow (Platform Type: SharePoint 2013 workflow) using SharePoint designer 2013.
• In this workflow I had to change the item level permissions for the item on which this workflow would be running
• And also need to change the item level permissions on the workflow task created through it.
• Prior to this August the workflow was running absolutely fine but suddenly the break role inheritance just stopped working and the workflow didn't work as expected.
• The item is accessible to all site members but this should not be the case as I tried to make it editable only by the creator of that item and his/her Manager.
• Also, the tasks are being assigned to a specific group say approver group so to make the task assigned to be editable by only approver group members I had again used the break role inheritance to achieve this
• The workflow actions are as follows:
  • To break the role inheritance: - [%Workflow Context:Current Site URL%]/_api/web/lists/getbytitle('[%Workflow Context:List Name%]')/items('[%Current Item:ID%]')/breakroleinheritance(copyroleassignments=false, clearsubscopes=true)
    • called this using http web services call action using POST method
    • supplied the request header digest along with Accept and Content-Type in the Request Header
  • To assign role/permissions to the item: - [%Workflow Context:Current Site URL%]/_api/web/lists/getbytitle('[%Workflow Context:List Name%]')/items('[%Current Item:ID%]')/roleassignments/addroleassignment(principalid='[%Workflow Context:Initiator%]',roledefid='[%Variable: ContributeRoleDefId%]')
    • In this the contribute role definition id is obtained using http GET method and stored in the ContributeRoleDefId variable and assigned using POST method.
    • all others are assigned the read role definition id.

Need a reason why this is happening and how to solve this issue.