I have created an issue from this discussion, as it is an issue. I'm still new to handling issues and stuff on GitHub so I don't know if this is the correct way to handle this, but I will answer it here, and if the problem gets resolved, I'll close both the issue and this discussion.

YT-DLP does this when downloading videos, have you checked if the downloaded videos have been downloaded without issues?
These are the main things to look for:

• is the full length of the video downloaded? Do not trust the video length that is displayed, look at the entire video yourself to be sure
• is there audio present?
• is the metadata there?

Nevermind, I read the filenames wrong... Could you go to the EXE folder and open the terminal, then run these commands to check whether it's the script causing issues or if it's something else (replace "<the-video-url>" with the video's URL):

• yt-dlp.exe -f "bv+ba/b" -w <the-video-url>
  (This command checks if it's a problem with YT-DLP or FFmpeg)

• yt-dlp.exe -f "bv*[height>=4320]+ba/b[height>=4320] / bv*[height>=2160]+ba/b[height>=2160] / bv*[height>=1440]+ba/b[height>=1440] / bv*[height>=1080]+ba/b[height>=1080] / bv+ba/b" --merge-output-format mp4 -S vcodec:"h264" -S acodec:"mp3" -o "%%(title)s.%%(ext)s" -w <the-video-url>
  (This command checks if it's a problem with the default args used with the script, not the ones that youcan change in VARS.txt)

• yt-dlp.exe --embed-chapters --embed-metadata --embed-thumbnail -f "bv*[height>=4320]+ba/b[height>=4320] / bv*[height>=2160]+ba/b[height>=2160] / bv*[height>=1440]+ba/b[height>=1440] / bv*[height>=1080]+ba/b[height>=1080] / bv+ba/b" --merge-output-format mp4 -S vcodec:"h264" -S acodec:"mp3" -o "%%(title)s.%%(ext)s" -w <the-video-url>
  (This command checks if it's a problem with the default args in the script + the default args from VARS.txt)