My experience with the usps tracking system is that it lags behind the packages actual disposition, and for whatever reason seems especially acute
with stuff coming from the Pacific Northwest to California. Many times, I have checked the tracking info and says that a packaged has arrived at the USPS hub that serves our area, with no departure shown from the hub (60 miles away), and then 15 minutes later, I go to the local Post Office to retrieve the daily mail from my PO Box (we have no home mail delivery service), and there it is in my PO Box.
So your explanation about them not being able to scan a package after 8PM would explain why the tracking info would show a package arriving at and still being in a hub, when in actuality, it's moved on and on the way or has made to the delivery destination.
And then there is my recent experience where I ordered a railroad documentary DVD from a shop that's in a town about 80 miles to the southeast of me here in the
S.F. Bay area. The package took a circuitous route down to Southern California, got to their hub, then made the rounds to a couple of city Post Offices, back to the hub in the Bay area where it started out from, sat there for a few day, and finally showed up at my local post office. All in all, a 10 day journey... and the dang address label was correct and very much readable. I have no clue and neither does the local Postmaster, why it got sent to Socal based on my zipcode.
I come to regard tracking info akin to the little disclaimer on the boxes of frozen entries, bearing a picture of large and luscious looking serving, and the words "serving suggestion" beside it.
Basically signifying that "this is a suggestion of what you'd like to or to hope to get, but it ain't here in this box".