What does UPS "UPS initiated contact with the sender to obtain clearance information. Once received, UPS will submit for clearance." mean?

We supply all necessary clearance information to UPS included with the shipment in the form of three commercial invoices. We also send this information electronically to UPS. Despite this, shipments often have the status "UPS initiated contact with the sender to obtain clearance information. Once received, UPS will submit for clearance".

In this situation, UPS never contact us, the sender, and the shipment usually, eventually, continues its journey. We can only think this is a delaying tactic when UPS can't process all the received packages in time to meet the promised delivery time.

In the early days we used to contact UPS when this happened but they always said they hadn't received the commercial invoices, when they had, and for us to send electronically. Now, we just wait because contacting them is a waste of time and achieves nothing.