Hm, I too primarily have srt's. No idea why just says "failed to load" or somesuch and I haven't been arsed to figure out why when I can just hop over to Plex and watch.

That said, I've had a few HDR movies which Jellyfin handled a lot better, so it's a bit here and there.

As for skipping, I primarily skip backwards when I miss dialog (so much mumbling these days), or forward when it's a TV show which has segments I don't care too much about, like say some irrelevant love subplot.