An Encoding Mismatch. The subtitle file might be saved in Western (Windows-1252) while your player is trying to read it in UTF-8.
Most modern media players (like VLC) allow you to manually adjust "Subtitle Track Synchronization." For a permanent fix, tools like Subtitle Edit can "stretch" or "shrink" the timings to match your video perfectly. 2. The "Mojibake" Menace (Encoding Errors) subtitle Gremlins
I can help you troubleshoot the specific error or suggest the best tool for the job. An Encoding Mismatch
Usually a mismatch between the Frame Rate (FPS) of the video and the subtitle file (e.g., a subtitle file timed for 23.976 fps played on a 25 fps video). Subtitles that are too small to read, bright
Subtitles that are too small to read, bright neon green, or stuck at the very top of the screen are often the work of hard-coded formatting gremlins.
If you want total control, convert your file to a "clean" .srt format. SRT files are plain text and usually let your TV or app determine the font size and color. Final Thoughts