re: A question for those with experience working with video in Photoshop

OK - here's my best guess (limited by my experience with video in PS). My hunch is you're processing layers you don't need, like all the layers except the top layer (Video Group 3). In your timeline, it appears that "Video Group 2" has no content. Yes? It looks like the only track with content is "Video Group 3". I would try getting rid of those excess layers (including the Black layer at the bottom; Layer 1) and give that a try. Again, my experience with Video in PS is limited. You might also try "flattening" the layers before exporting just for kicks.