Subtitles work if file is on my ssd, but they don't work from a external hard drive

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Title of the post, i'm having this weird issue where subtitles display perfectly on client devices (fire stick 4k and android app) if i run my media from my server's ssd (with my server being an old laptop that has both a quicksync capable igpu and nvenc via the nvidia gpu) and i can't seem to understand why, like, i'm at a complete loss as to why subtitles don't work from the external hard drive but do from the ssd despite using the exact same files