I’ve found a missing piece in my definition of the “setup” phase at the beginning of the scene. That piece is “what’s already happening”. I’ve been searching for the right wording for that, for years. I think that’s it.
So, in the first moments of the scene, the setup phase, your only job is to discover/determine:
What kind of people are you
Who are you to each other
Where are you
What’s already happening
No need to be funny or even interesting at this stage. Just find/decide these things, and go from there. Once you know you’re two friendly bishops on a rowboat waiting for the fish to bite, you can keep building. Add points of view to the characters. Those will lead to emotions. Which will lead to action. Will will change the initial setup. Which will constitute a scene well on its way.