Hi, so I am unsure as to where the problem lies, all I can see is that Glyphs crashes. Digging through the archives, this topic seems to explain that the RMX Scaler is not designed to work with brace layers. Nonetheless, attempting to do so results in a complete crash of Glyphs, so I thought it might be worth noting.
Example. I am working with the RMX Scaler to create a synthetic condensed. All letters work fine, with a few exceptions: for instance, when exporting my font (two axes, weight and width), the miniscule e, which of course has a brace layer around 150 stem weight for contrast reasons, interpolates in a funny way as the brace layer on my width axis still has the regular width.
So far, the workaround would be to create a seperate glyph, copy my brace layer into that, scale with RMX and then paste it back into my brace layer. Which is fine, I merely wanted to report this crash issue. If there is any other workaround people have found, please do let me know! Thanks!