Parcels Delivered to Amazon but returned to DPD Depot a week later

Hi, I have what seems to be a very bizarre case. on the 28th of February all parcels in my shipment were delivered to Amazon with stamps/signature. However, on the 9th of March 141 of these parcels were returned to DPD and delivered to the DPD Depot. Has this ever happened to anyone/does anyone have any idea why this has happened?

Thanks!