Not able to Receive an RMA in Inventory

Once in a while I came across some simple and silly issue.

Recently my customer escalated that he is not able to receive RMA against a Sales Orders. he reported that after entering and BOOKING RMA , he was not able to receive item in the warehouse and there were 500 + such cases.

Customer created Sales Order with Warehouse W1 and shipped the good, and then they created RMA for same item in W2 and book , but not able to receive ( a valid test case).

Initially I thought it is due to some custom code , but actually it was not related to any customization.During further analysis I  observed that I am able to Book and receive RMA in warehouse W1 but not in W2 , and it is due to the fact that Item was not assign to warehouse W2 and this whole issue was because of this missing assignment.

And FIX was just assign the item to warehouse W2.

Technical Solution
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SELECT l.shippable_flag,m.shippable_item_flag
   mtl_transactions_enabled_flag
    FROM mtl_system_items m, oe_order_lines_all l
    WHERE m.inventory_item_id = l.inventory_item_id
    AND m.organization_id = l.ship_from_org_id
    AND l.line_id = &Enter_Order_line_id
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Execute the above query and if it return data ,it means item is assign to warehouse , but if above query don't return any data then go and assign item to required warehouse.

In the above query I am checking  conditions
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m.inventory_item_id = l.inventory_item_id
    AND m.organization_id = l.ship_from_org_id
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to validate if item that define in ship_from_org_id in RMA is assign to the Inventory organization in INVENTORY