Jellyfin Roku "skips" 2/3rds of film even when "play from the beginning" is selected

Going to try and include as much detail as I can. Searching online got me mostly tangentially related issues.

I don't know if this is important information or not, but this issue is occurring with my first "alternate version" film, specially "Little Shop of Horrors (1986) - Director's Cut", formatted exactly like that in a folder alongside the Theatrical Cut, following the official docs here: https://jellyfin.org/docs/general/server/media/movies/#multiple-versions

It plays from the beginning fine on the server pc; Windows 11, played through Firefox. The Theatrical Cut plays fine on both.

In the Roku client it skips about 2/3rds of the film and plays from there, even if I choose "play from the beginning".

I have Trickplay images enabled. The images generated for this film appear to be correct (the first image is the beginning of the film, not the the point that it's erroneously playing from).

I do have the Intro Skipper plugin installed, and I'm wondering if that's the cause. I do see the long grey "credits" part highlighted on the seek bar, and there's also a tiny part at the point where it begins playing midway through that shouldn't be anything significant warranting that. I skipped back a bit and there is like a tiny black cut during a shot change, not sure if that's a rendering issue or not.

Is there a way I can delete just that possible detected spot somehow to see if that fixes it? I'm not knowledgeable enough to understand how that works currently.

Anyone familiar with issues like this and know a potential solution?

Thanks for any help.