Very old post, but I think I found the mistake.
Yet I want to know if there is somebody with the solution.
The problem is that the block itself has a nested block with the same name, which contains the attributes. It is not possible to see them by using the block editor. I was able to see it when I used the refedit command, then I could see the the attributes in the background, so I listed it and it has the same name.
Attached an example of one file I was working on with the same mistake
Greets