Hi Craig,
The scene seems like a collage from different artists. Some constructions made me wonder what they do. A XPresso misses an object and has so invalid connectors.
However, the main problem seems to be based in the use of the Standard Particles. Keep in mind that particles need to build up over time. If you like to have them at any time exactly as expected, they need to be cached.
The “Editor View” is refreshing many times if you stay at the same frame. Sometimes pressing the “A” key does this refreshing as well. This is needed to keep “you” working, while things are processed in the background.
The “Picture Viewer” is a with very little exceptions a one time run trough the frame and process the given parts. Having said that, typically, each object has a very specific position in this process, based on Priority settings or position in the Object Manager. For the rendering this is not a cycle-like process as in the Editor view, the data is available or not. If not available, the data is taken from the frame before. If something like that happen, a chain reaction might occur. I had examples in the past years here on Cineversity where three frames delay were established based on ignoring that process priority. Again, this doesn’t show up in the Editor view, as it cycles through.
So, two things need to be acknowledged, processes which are build up over time and which are not cached might show up differently in Editor and Picture Viewer. Caching and baking is the key here. Baking stands here as well for the turning processes into keyframes. Secondly, priority, priority ....etc. Kai has produced fro Cineversity a Priority series, which I consider as a “must see”—“must know”! There is no way around, if you work with complex scenes like the one you send to me.
My best wishes
Sassi