Failed when muxing audio

Hi,

I receive the following error while transcoding a movie file:
17:22:30.304: [encode] video: encoded 6910581547 bytes
17:22:30.304: [encode] audio: encoded 0 bytes
17:22:30.304: [encode] muxing overhead 3519308 bytes
17:22:30.309: Exiting... (End of file)
17:22:30.445: (!!!) Encoding finished too early, only 96% processed.

It appears it is unable to mux the audio file. There are no options for audio is the transcoding tab. Can someone advise how I can resolve this? Incomplete video plays fine but without any sound.