I've tried playing back the rendered video, and it just abruptly stops at 25 minutes, even though I'm trying to render a 56 minute video. I used to use Vegas 14 and this never happened, so I'm wondering why the render will not complete? It's been stuck on 100% for around 40-50 minutes now. The elapsed timer isn't going up anymore either. Here's a photo of what the rendering tab says, in case you need it.
Embed the photo here (this is possible with the icon to the left of the smiley). No one likes to be redirected to other pages unless absolutely necessary.
Does this occur in exactly the same place every time you try? If so, try to figure out what could be causing problems at that point.
Did it run out of room on the c disk? Keep at least 2x the final render file size free. Otherwise what frame did it stop on- consider re-encoding the media there, replacing it and trying again.
Patience.
For sure, patience. And look at Task Manager to see if the hard disk is being written to.