An application auto-updates to a newer version that expects a different FFmpeg API (e.g., upgrading from FFmpeg 5.x to 6.x). If the installer fails to update the DLL, you get a version mismatch. Conversely, manually replacing the DLL with a newer or older version can break compatibility.

While most modern applications reference DLLs locally, some older software expects DLLs to be in the System32 or SysWOW64 folders or listed in the %PATH% environment variable. If the DLL resides elsewhere, Windows cannot find it.