Sounds like strange behavior.
While I don’t really care for the Fire TV stick, Amazon UI, or the Preview app(I prefer Roku), I did give it a try.
If you are in the recordings menu and position on the program tile and there is one recording(a movie) paused at 40 minutes and you hit the OK button you end up with a menu with options Watch Next and Watch. It appears that both of them start at the begining. And I have no idea which one should be resume.
Using the play button seems to resume.
I also noticed that the app goes into sleep mode rapidly when in a menu. So while I can see the Fire version I don’t see the last OS update date. So who knows
fixed the description a little.