Must be clients behave different than the web UI.
In my case I have multiple episodes from 11 shows.
The oldest episode (OAD) for each of the 11 shows appears in Up Next.
This is how they're sorted and I see no pattern/reason for this order.
## RecordDate Title
1) 2020-01-29 Expedition With Steve Backshall
2) 2019-11-09 Impossible Engineering
3) 2020-02-01 Seven Worlds, One Planet
4) 2020-02-13 Hidden Gems of Turkey
5) 2020-02-05 NOVA
6) 2020-01-21 Frontline
7) 2020-01-16 Reclaimed
8) 2019-09-29 Alaska: The Last Frontier
9) 2019-08-17 Man, Woman, Wild
10) 2019-09-14 Ocean Mysteries With Jeff Corwin
11) 2019-11-05 This Is Your Day
## OrgAirDate Title
1) 2019-07-21 Expedition With Steve Backshall
2) 2019-11-09 Impossible Engineering
3) 2020-02-01 Seven Worlds, One Planet
4) BLANK_NULL Hidden Gems of Turkey
5) 2020-02-05 NOVA
6) 2020-01-21 Frontline
7) 2020-01-16 Reclaimed
8) 2019-09-29 Alaska: The Last Frontier
9) 2011-09-09 Man, Woman, Wild
10) 2013-10-12 Ocean Mysteries With Jeff Corwin
11) BLANK_NULL This Is Your Day
So, the oldest unwatched would be Man, Woman, Wild if it went by either recorded date or OAD.
I don't watch the shows/episodes from clients or the web UI. Maybe that's why there in a wierd order.
I watch them outside of Channels using VLC (variable speed playback) or edit adverts out and archive outside of Channels.