Workflow PostScript not working

Hello Experts ,

We are on SAP Sourcing 10 . We are using workflow for project documents. Currently we have a scenario where certain checkboxes have to be checked immediate after the approver approves the project document .

To accomplish that , I have created postscript in workflow which will check if the document is approved and then check the checkbox . However , I see that the checkbox is not getting checked after approval . However document is moved successfully to next stage and getting unlocked . Checkbox name is - Z_WF_COMMGR

The code in postscript -

// getting project home

projectHome = IBeanHomeLocator.lookup(session,com.sap.eso.api.projects.ProjectIBeanHomeIfc.sHOME_NAME);

proj_id= doc.getDocumentId();

myProjHome1 = IBeanHomeLocator.lookup(session, ProjectIBeanHomeIfc.sHOME_NAME );

relProjectIfc = myProjHome1.findForEditByUniqueDocName(proj_id);

if (getApprovalStatus() == APPROVED ){

try{

projectHome.upgradeToEdit(doc);

relProjectIfc .getExtensionField("Z_WF_COMMGR").set(true);

}

catch(e){

logMsg.setLogMessage(e.toString());

logMsg.setException(e);

Logger.error(logMsg);

}

}

When I check the log I see the below info but the workflow owner has all the rights to change the project document .

Exception:

com.sap.odp.api.common.exception.ApplicationException: You cannot view the document because you do not have sufficient permissions. Contact the document owner to request access to it.