Subtitles don't disappear at end timestamp

Watching several movies lately via the iOS and Apple TV clients, I was (slightly) dismayed to see that the final subtitle entry is never removed from the screen - and therefore remains visible through the end of the movie (over the end credits). Seems to be repeatable 100%.

As an example: Watching “Rogue One”, the final line of dialogue (“Hope.”) remains on-screen throughout the display of the final credits. Looking at the associated data (embedded subtitles in an .mp4 container, but occurs with separate .srt files, as well), I see this entry displayed as:

1536
02:05:33,052 → 02:05:34,486
Hope.

In other words: Subtitle index #1536, should be displayed at 02:05:033,052, and then suppressed a bit over a second later, at 02:05:34,486. But this final end timestamp is not respected by the Plex client, and the final subtitle remains on-screen … again, through the display of all ~8 minutes of end credits.

This does NOT appear to affect the web client. Any ideas what is going on - and/or how best to report details on this bug, so the developers can address it?