The P.O., UPS, FedeX, DHL ( they are back, it seems) all break things, occasionally. I have found UPS to be the worst, with the P.O. the best among the "majors" that I see. FedEx, I don't recall.
But, I can say with certainty that more of my items, particularly heavy ones (our bread and butter), are damaged by poor shipper/seller packaging than by the shipping services/companies. Had a guy send a nice Pre-War AF O-gauge steamer from Seattle to the Gulf Coast years ago, packed in a box and a few ounces of shredded newspaper. The box (the P.O.-handled part) was fine; the loco was shattered. Then there was the KTM brass 2-rail, unpainted J3a Hudson - with the partially crushed cab, for much the same reason.
There were others.
Fortunately - so far! - all of this, regardless of the "fault", has been rare.