That literally shouldn’t be possible with dummy rounds. They should be a solid block inside so it’s impossible to load with powder. If that’s true then Starline deserves to be sued into oblivion.
I think you’re mistaking blank rounds for dummy rounds. Also a quick look at their website shows they sell brass. Brass for reloading, for live, for blanks, or for creating your own dummies.
Again, there is no way to test a round to see if it’s a dummy short of attempting to fire it. Normal ones are a completely different color or even transparent for this reason. Obviously that doesn’t work in filming.
As to which producer is culpable, Baldwin absolutely could have fired her and was part of violating safety protocols by ignoring complaints he could have addressed directly and immediately.