watchOS/Downloads: reports of downloads on watchOS being corrupt/put together badly

### User report

On my Watch, sometimes the downloaded episodes are "corrupted". The audio at the start will be of the episode already in progress, and after a couple of minutes the episode will go on as normal, thus skipping the first few minutes. Like, instead of playing [0 1 2 3 4 5 6 7], the episode goes [3 1 2 3 4 5 6 7].
It doesn't happen every time, so I just delete the file and download again, but it's annoying if it happens when I'm on-the-go (my Watch is wi-fi only and I don't take my phone with me every time).

I'm using an iPhone XR and an Apple Watch Series 5 GPS. Both are using the latest iOS/watchOS, and this has been happening for months, even before iOS 15 / watchOS 8

My current Wi-Fi is 5GHz only, so the Watch can't connect to it. All the sync/download on the Watch happens through Bluetooth.

Start by reproducing the reported watchOS download behavior with the stated iPhone XR, Apple Watch Series 5 GPS, and Bluetooth-only transfer conditions. Done means downloaded episodes consistently play from the beginning without duplicated or skipped audio; the report names no source files or tests to inspect.

Written by the indexing model from the issue text.