I have an assignment where I need to create a bunch of stand alone videos, and finally one large video, made up of the stand alone videos. For efficiency, I'm nesting the stand alone videos in sequences and then bringing those sequences into a final sequence for export. Therefore, I should only have to render once, and from that sequence export my stand alones. and the larger video.

What's strange is that after a couple hours, that final sequence which I just rendered, goes back to being red (unrenderd). It doesn't prompt me for missing preview files or anything, it's as if they just vanished.

I did notice as I was rendering, it said "Indexing rendering" and had a string of letters and numbers. I don't recall ever seeing this before, and I don't know what that is.

Any help solving this mystery or workflow suggestions are greatly appreciated.