It’s persistent but I might have more clues. v2 and v3 up next look as expected. iOS app and my watchlist on Kodi both have the Grand Tour episode showing. I checked Hidden/dropped and this is a hidden episode.
As far as I understand it, “hidden” isn’t taken into account. Only dropped. Though if app.trakt.tv isn’t showing the same as the iOS app then something is still unexpected there.
I never really understood the dropped vs hidden discussions/controversy. As you can see, I didn’t use it much anyway. The issue isn’t a problem for me, just thought (know) you want consistency across platforms. I won’t change anything if you want to work through it, or I can just drop the show and it’ll be fine for me. Just let me know what you want to do.
I tried to reproduce the issue by marking the first 5 seasons as watched, and then hid season 6 from progress in v2. On my end I’m seeing what I expect:
S6E1 still in both iOS (version 3.2) and v3 web (app.trakt.tv), while v2 is no longer showing it.
While I can’t be sure why you’re v3 web isn’t showing it, my only suggestion would be to try clear any browser cache or try a different browser and see if it’s the same.
Either way, right now the v3 solution would be the drop the show, and it’ll return if you add another play to history later. Also if, say, you decide to pick it up again from Season 7, v3 should implicitly “skip” season 6 anyway.