PM Work Order not to delete PO after TECO

As standard SAP Work Order process

there are three cases:

1- WO created --  PR created-----------------------------------TECO, PR deletion indicator

2- WO created -- PR created  -- REQ created--------------TECO, PR deletion indicator

3- WO created -- PR created -- PO created-----------------TECO, PR deletion indicator (to remove deletion indictor)

after doing TECO for each stages, PR is set for deletion flag.

For case 3 and once Maintenance reopening the Work Order for invoicing and PO is there,  PR workflow will get reset from the beginning.

I want to stop PR deletion flag in case 3 once PO is there, so when Maintenance reopening WO,  PR would not reset the workflow and PR will not go for further process.

thanks.