FFmpeg now has the capability to concatenate files internally, you might have better luck with that. It works as follows:
ffmpeg -i "concat:inter1.mpeg\|inter2.mpeg\|inter3.mpeg" -c copy interALL.mpeg
If that doesn't work, you may need to remux them to mpeg transport stream files first:
for f in inter*.mpeg; do ffmpeg -i "$f" -c copy -f mpegts "$"; done