Hello Mahavir,
Have a look at these SAP Notes look relevant to your situation:
1824067 - Avoid/Correct Double Status ESTO INST for IS-U Devices.
549414 - Equipment status does not change after delivery creation.
Other notes seem related
1660754 - HT-SW: System status not updated after invoice creation.
1827815 - Inbound processing of serialized equipment failed.
Good luck
KJogeswaraRao