Thanks for your responses so far!

I should have done this in the first place, but I've uploaded a few images of the fit here, trying to demonstrate the fit issue around the shoulders.

Does that provide any further insight? It just kind of feels like the shoulders are a bit stiff, and I'm worried the body of the jacket moves too much with the arm/shoulder when I raise my arms. Not sure if this is just what suit jackets do, or if it's an issue related to the fit of the jacket.