Bare in mind there will always be sorting errors, a package that goes by air to the wrong country, gets redireced, could have done a lap of the globe and you may still get it 10 days, and we are non the wiser. If it goes in a container, then on a slow boat to wrong country, then ditto when redirected. It could turn up after who know when.

Even domestic parcels get dropped in the wrong sack all the time. Thats probably the biggest cause for delayed mail.