So I think I found your scene. I’m at the 1 hour 20 minute mark. The scene has bullets flying through the air. Those are just moderately audible. However, bullets hitting cars are very audible. If we’re talking bullets striking the shield, EXTREMELY audible. There is an increase in pitch toward the end of the scene you specifically mention. I found it to be a very satisfying listen. I’m on Disney plus watching in Dolby Atmos. Hopefully you find the same experience and don’t find unboxing and reconnecting to be a waste of time. 

Do the bullets hitting the shield shift left to right? Or just centered in front of you? Should be expansive movement  

Today i listened scene from the winter soldier. Zero l/r effects. As you say it’s sound like “telephone booth directly in front of the screen”.

true hd atmos

Unfortunately I have not seen this movie in theaters. Nor did I hear it on my other high end soundbar which I’m still waiting to be returned from its repair. So I have no means of comparison. 
 

I have done trueplays after each update because the sound profile was definitely weird each update. Including the recent one. I can definitively say I’ve heard certain improvements in ambient sound. 
 

Now to the movie. The bullets fly off the shield and the sound is enveloping throughout the room. But as one who has not seen this movie before now, the bullets deflecting do not have an ambient sound of deflecting right to left back toward the gunman. That sound is very faint like as in I had to put my ear next to the bar to hear it. I would trust the previous posters judgment regarding the movie. D700, my feeling, again without data to back it up, is that sound intended for the L or R channels is now more increasingly being mixed into the center speaker array than it was previously. Which would account for certain ambient sounds that I know for a fact I’m hearing now that I did not hear before. But to support yours and the previous poster’s point, if there’s definitive L—> R sound that the Arc Ultra is not accurately outputting then more work needs to be done. 

Of note, I have two arc ultras. One in the living room with sub 4 and 300s as surrounds. In the bedroom I have sub mini and 100s. The living room one has experienced changes in sound with each of the last three updates, each of which for me had required trueplay to balance it back. The latest one I went from about volume 15 to volume 25 to get a similar volume level. After trueplay it reverted back to normal. It feels like something is happening. But whether that something accounts for all the issues is another matter. I can say I went from extremely dissatisfied with the arc ultra to at least pretty pleased with how it handles sports, which is what I mostly watch. I just don’t know if that difference accounts for complete mix accuracy, which I feel my other soundbar had. Still waiting for its return via UPS. Not sure if I’ll set it up or not. I hated the bass on it. Loud, boomy. My fav thing about Sonos is the rich levels of bass you get with Trueplay. 
 

Finally, I don’t know if you’d find it worth unboxing and trying again based on my info. I don’t really want to be the reason you unbox and feel like it was a waste of time. But I’m also curious if you’ll detect any change in effect. 

So, hey, Sonos, forget about the Atmos test files. Focus on delivering cinema sound. Here’s a great example for you to work on.

I’m listening on Disney plus. For me the effects are all over the room. Including this specific scene. Like I said idk if I’m missing the L-R separation to which you refer but it definitely does not sound like it’s in a closet to me. I can also distinctly hear bullets strike two of the gunmen if that helps.