Glad to see this analysis develop on!!!
I definitely saw the bird in a pre montene feel, scenes as white winged tanager and white-plumed antbird on the same site were not unusual .
The bird in question also has a kind of streaked under site, I never really took a close eye to flycatchers on...
I agree on the first three pictures being Slaty-capped, the difference in wingbar colour is probably a difference in subspecies.
However I am not quite sure on the last bird too, for comparison I added two pictures of plumbeous crowned where you can see a clear difference in...
Maybe you guys can help me ID these Ecuadorian Bristle tyrants.
The first picture was taken on the west slope (around 1300 m), I'm thinking Marble-faced given the whitish wingbars.
But the next two pictures are from the east slope (same elevation) and the bird has real buffy/cinnamon...