ffmpeg: How to fix `Unsupported channel layout "1 channels (FL)" error`, when I convert the source containing separated FL/FR audio streams?
No need to use pan filter, you can reassign channel layout using the channelmap filter.

ffmpeg -i ticket1474.mov -af channelmap=0 -b:a 128k -map 0:v -map 0:a -y sample.mp4


See docs for channelmap filter.

I've skipped mapping the timecode track. ffmpeg will set it as metadata in the input file, and the MP4 muxer will pick it up from there.