Brace trick problem in two dimentions

Hi! I’m trying to use the brace trick in a 2-dimentional font, but I’m getting unexpected interpolation issues.

I have the following masters (2 weights per 3 widths):
100, 50
100, 150
100, 200
900, 50
900, 150
900, 200

And adding the brace trick layer at {400, 2o0}, aka Bold Extended. And for some reason it makes {400,…} position equal to {100,…} for the other two widths. In other words, I’m getting Light weight in the middle, where it should be Bold.

Am I using the brace trick incorrectly, or is it a bug?

This is not supported in Glyphs, yet. Only switching on the first master is supported.