I dont't think there is any rule what still works and what doesn't. In the "sale" 2 days ago I bought (Amazon Prime Video) the 2 seasons of the Sarah Connor Chronicals. Which is available on Amazon since a few years. Season 2 I could download no problem in H264 1080p. With Season 1 only 5 out of 9 episodes could be downloaded (also in H264 1080p). This was with version 6.1.6.1. Version 6.1.6.5. would download the missing episodes in SD, however, the quality is less than the DVD version. Attempting the episodes which worked with 6.1.6.1 would also only downloaded in SD.
The same applies also to older movies which have not been shifted between channels. Is it possible, that Amazon is already converting existing material to the new DRM?
Kattanders
Yeah, that's basically the same thing I was experiencing. 6161 would download some episodes while others in the same season got the "unable to access video information, please check your internet connection" message. 6165 was able to download those failed episodes but only in 540p. There were also videos that couldn't get analyzed, again 6165 fixed that but only in 540p. I guess right now the only thing we can do is wait and hope the devs will be able to crack this.
It's unfortunate, I subscribed to Crunchyroll in prime channel during their promotional sale last Christmas ($1.99 per month for 2 months), was trying to get through all my anime backlog before the end of the promotional period, but looks like I'll need to extend my subscription for at least another month.