The problem is that they are now using USPS rather than UPS for most of their Prime shipments. UPS isn't perfect, but at least their tracking is close to 100% accurate. USPS tracking is very hit or miss. I have actually checked USPS tracking at the same time at both Amazon and the USPS website and have gotten more current info from Amazon.
That's gotta be part of it, Rich.
Weirdly, I had one package from Amazon recently start out as a USPS delivery...miss it's deadline by several days...Amazon told me it went missing and gave me a full refund (and this was a $45 Batman TV Series Blu set!). But tracking remained active...and it switched to a UPS tracking number...and then several days later it arrived--via UPS! But the Amazon rep told me clearly that his info told him it was lost in transit. Tracking told an entirely different story. I didn't know WHAT to think about that one.