Probably not a cinematics/media specific question but that’s what I’m working on…
Every time I save all, it prompts me to save about two dozen materials that I did some tests on ~2-3 weeks ago but didn’t save (and don’t actually want to modify). It’s super annoying - but I don’t want to create new revisions of all these files on perforce because there’s no actual change.
Where is Unreal keeping track of what files are dirty and what aren’t? Would love to just nuke it and clear the slate.
The editor see a connection and usage hierarchy between all your assets, you can see it by right-clicking an asset in the content browser and choosing ‘reference viewer’.
Sometimes, the dependency between assets is not obvious.
It sounds like you have an ‘asset chain’ somewhere, so when you change one thing, everything that depends on it has to update.
It’s a good idea to save, otherwise you might be back on here with one of those ‘hey, I opened my level and it’s totally empty!’ questions… 
Ah, this is definitely not the case in my scene. I can load up my unreal project (which is in a “clean” state - perforce has no pending changes, etc.), and do nothing but:
load a level
load a level sequence
And immediately unreal reports “10 unsaved files”. And it’s been the same 10 files for the last few weeks.
I have another copy of my project on another machine, and on that one I don’t have this problem (and the other artists on my team don’t see my list of dirty files, though most of them have 2-3 different files that unreal is always bothering them to save instead). So there’s something, somewhere, which is confusing Unreal - it thinks these files are dirty immediately and it’s not clear why…
Then I’m not sure, sorry 
I see this happen with Perforce constantly.