Bracket switching letterforms will not change in variable font

I can’t get my variable fonts to switch to alternative forms, when the alternate layer is not compatible with the normal layer.

I have some alternates going in an optical axis, and the variable fonts will not switch to the alternative forms – and I think it’s because the bracket layers are not compatible with the normal layers. Because when they are, the substitution works. All the normal layers and the bracket layers are compatible with each other.

Using FontGoggles I can see that the font is switching to the *.varAlt01 alternates, but the outlines stay the same.

I have put in the custom features:
Feature for Feature Variations custom parameter with the value: rlig
Enforce Compatibility Check: Yes

They did nothing.

All the normal instances work fine.

What am I doing wrong?

Could you post a screenshot of the Layers palette for one of those glyphs?

First the normal form, which is a curvy tongue:

And the alternative optical substitution is a straight tongue:

Note that both the ‘C’ and the tongue are components, but only the tongue have the same switching layers as the composit glyphs (come to think of it, is that the reason?)

Can you send me the file?