I had an issue where USPS was claiming packages were delivered to meet their prime contractual agreement then not actually delivering it until 1-2 days later. (So prime 2 day was taking 3-4 but marking it as delivered to my box on day 2 every time). I filed a complaint to USPS, and a USPS employee actually called and admitted that they were probably doing that to make their stats look better. I feel like any other organization admitting to contractual fraud like that would actually face consequences, but truthfully I don't think anyone holds USPS to a high bar.

Contacted Amazon and they claimed they prioritized UPS for my address. Seemed to work -- packages come via UPS almost exclusively now. Pretty good resolution in my book.