This is strictly an Amazon issue, and YES, I have the same problems.

A while back they Roku Amazon Prime app was drastically changed. It was changed to the common interface that the Amazon Fire TV has. And I for one hate it. It's now slow as molasses, confusing and works very poorly. Everyone has the same inconsistent watch next list issues. This version offers fewer features that the old version had. When done with a show and wanting to choose another one I often find it easier to jump out of the app completely and go back into it rather then back out to the home page with the remotes buttons - BACK (wait, wait wait) BACK (wait wait wait) BACK (wait wait wait), or press HOME and then select AMAZON again and put up with the slow loading.

What totally pisses me off is the complete lack of a way to mark a series as UNWATCHED. We watched completely through several TV series and started over with them. ALL seasons and episodes show as watched and the default selection jumps to the last ep of the selected season. I have to look back and read the synopsis to figure out where I left off - IF I remember. Even then it sometimes jumps to about where we last watched it last, like partway through the closing credits, and does not start from the beginning of an episode. I have to remember to move to the WATCH FROM BEGINNING button and choose it. Support offers no solution. Taking the series OFF the watchlist for a few days or weeks sometimes marks it as unwatched. Most times it does not. I've been an avid Prime member for years. This just really blows.