When I start a show with Up Next and then try to delete it, it doesn't work the first time unless I've watched the whole show. I have to do it a second time for it to be effective on a partially watched show.
How long are you waiting for the show stop showing up? Also, some panels don't update till you leave and return.
happens to me too, on the iPad app as well as Apple TV.
Typical use case: stop watching when the end credits roll. Go back to delete it and move to the next episode--I have to delete twice.
At least it's not just me 