: Ensure every numbered segment (001, 002, 003, etc.) is in the same folder. Use a File Joiner :

: If a file displays as a solid color (often red on macOS), it may be due to a codec conflict or a Big Sur-related rendering bug. In such cases, using an updated codec pack like K-Lite can resolve the issue.

: The first part ( 001 ) often contains the essential header information required for media players to recognize the file format.