I have managed to capture it this time
It seems to start after something like 5 hours of rendering. This total video in this case is around 5hrs source, 30hrs render time.
I am applying brightness/contrast, colour correction, NBFX lens correction. Plus the track with the timecode (which is done as an event FX, text media, with empty text).
One can see that what is happening is that Vegas drops out the colour correction and the lens correction FX, momentarily.
I will finish the render (no usable output file is generated otherwise) and will see what the result looks like. Last time it was progressively corrupted. However, the timecode (bottom right) always comes through perfectly.
It seems to be fairly random, doing a number of frames one way and then a number the other way.
The other thing I noticed is that the preview is not running in the mode I selected, which was the default low-res mode. This selection took place right after the render started and I tried it several times.
The render was started after a fresh PC reboot.
Machine: i7-970 6 core, win7-64, 64GB RAM, 1TB HD. Graphics: GTX-750 Kalm 2GB.
I will also try doing the same job with MSP12. A few years ago I did 100hr renders on MSP11, on a 1GB winXP machine, without a single glitch.
GPU acceleration is disabled in the global config. Pro 13 did not work with that at all. It also doesn't seem to depend on the render format; I have seen it with several different ones. The fact that the timecode was always perfect in the output file tends to confirm that the render format is not the issue. The project was always 1080P 50FPS.
It may be that just loading a certain total size of media messes up the program.