Thanks to the owner of a jailbroken 2019 NanoCell who reported this on Reddit: moving between seasons dropped the focus onto S1E1 and never got past the second tab. Both halves of that were real bugs.
Season tabs no longer steal the focus. Changing seasons was wired to the focus resting on a pill, and it moved the focus into the episode row — which took you out of the tab row, so the third tab could never be reached. Resting on a tab now scrolls the episode row behind it and leaves the focus where you put it. OK still jumps you down into the episodes, and coming back up returns to the tab.
The episode list is no longer capped at 24. The list spans every season at once, so any show past 24 episodes lost the rest — and the season tab, unable to find its target, silently did nothing, which is where the jump "back to S1E1" came from.
Verified on a rooted TV with Black Mirror: the focus walks from season 2 to season 7, and season 7 opens on "Common People".
Install with the webOS Dev Manager or ares-install, same as the previous builds.