View part stocks from third parties into Spares Management

My customer has an issue to view service parts that were sent to external supplier for repair. They use a list of carriers to remove the parts from the internal inventory (warehouses and/or technician subinventories) and to ship to the external repair suppliers.

Problem is that they don´t have the visibility of how much parts are effectively shipped to external repair suppliers, due to failures in the transportation process (parts can be misplaced, broken, etc) and, for this reason, replenishment planning will be affected. And the reverse flow (from external supplier from internal stock by carrier) is affected, also.