Custom Workflow Activity is not working in Production environment

Hi All,

Can anyone help me out of the below issue:

I have created custom workflow activity to check document library when item is created, to verify that item and moving to other site collection library based on our requirements), workflow i have chosen automatically trigger when item created.

Actually this activity worked perfectly (without any exception) in development and uat environments. while moving to production environment i am getting below exception:

Production envronment architecture is One appserver +2 front end servers + 1 search server + 1 database server.

Also i have found one more issue: when i am uploading 10 documents into library, activity is identifying only 8 or 9 items only.

Thanks

Subramanyam

---------------------------------------------------
Class: CustomWF, MethodName: ActivityExecutionStatus Execute
Item does not exist. It may have been deleted by another user.
---------------------------------------------------
   at Microsoft.SharePoint.SPList.GetItemById(String strId, Int32 id, String strRootFolder, Boolean cacheRowsetAndId, String strViewFields, Boolean bDatesInUtc)
   at Microsoft.SharePoint.SPList.GetItemById(Int32 id)
   at CustomActivity.<>c__DisplayClass2.<Execute>b__0()
   at Microsoft.SharePoint.SPSecurity.<>c__DisplayClass4.<RunWithElevatedPrivileges>b__2()
   at Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode)
   at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(WaitCallback secureCode, Object param)
   at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(CodeToRunElevated secureCode)
   at CustomActivity.Execute(ActivityExecutionContext executionContext)
---------------------------------------------------