I just got my 37 minute long documentary made. On the 12th minute mark there is a clip and a bit of space and the next clip. I have tried to put a fill in between the space with another clip in order to fill in the space, but nothing seems to be working. The project only burns the first 12 minutes. The clip that it stops at and the clip that follows it are the same clip I copied and pasted the clip following it.
To remove the black gap select the clip to the right of the gap, click the Transition button bottom left of the selected clip and change the transition to 'Cut' . This will remove the gap and close up the clips.
The only way I can see you get 12 minutes burned to disc is if you are exporting the video and have Export selected range checked.(see image below) and then using another program to create the DVD.
AFAIK burning to DVD with MEP will use all the timeline.
In Timeline Mode and above the chapter markers line, there is another line with to markers like {}. These are supposed to be the starting and ending markers for the entire video. Check if the } marker is beyond 12th minute.