Hi,
Can you try and burn to disc as well please?
What you are doing is helping to isolate section of your system and eliminating others. So far the write process to a folder has been tested and works. Repeat and burn to disc will isolate the burn process for those file types.
The next stage will be to see if your burn issue is being caused by a corrupt video file within your project, isolating and identifying it.
Please attach screenshot of your project and free up space on your C drive.
Guides: PART E & F and you already have the link.