Subtitles don't work on certain devices

Hi everyone. I have Plex server installed on a linux laptop (core i5, 2.5ghz, 4gb ram). The problem I have is that enabling subtitles will not load the movie/show on certain devices. The subtitles work fine when watched on my Win7 laptops, but using my Roku tv, or PS3, enabling subtitles will not allow the movie to load and eventually fails. The subtitles are in .srt format. Like I said, it works fine when watching on my Windows laptops. And it used to work both on the Roku TV and the PS3, but then stopped working months ago (9-12 months I estimate). I do have the latest version installed, and always install new versions as they come out and test it to no avail.

I’ve read several threads about subtitle problems, but they don’t seem to be the same issue, as it works great as long as I watch on Windows. Any help would be greatly appreciated!