VDR Streamdev Plugin

Looks like the remux process is aborting. But in this case the log should contain much more than just this line, at least when running with full log output (VDR option -l 3 which is also the default if no -l option is given)

Maybe add a "2>>/tmp/ffmpeg.log", so you can check for ffmpeg errors in the log.
You could also redirect stderr to the system logs. Just insert this before the ffmpeg call (probably requires bash as shell):

  exec 2> >(logger -t "vdr: [$$] ${0##*/}" 2>&-)

I'm quite sure that ffmpeg is either gone or has at least closed its input channel. Maybe you have several ffmpegs running in parallel? A possible cause could be that your script doesn't handle HTTP HEAD requests. That's why I asked for a verbose VDR log.

I have added this to my script and got rid of that messages:

if [ "$SERVER_PROTOCOL" = HTTP ]; then
echo -ne "Content-type: video/mpeg\r\n"
echo -ne '\r\n'
[ "$REQUEST_METHOD" = HEAD ] && exit 0
fi