Interpolation inconsistency

I am working on a typeface with 2 axes: width and weight.

When adding intermediate layers to control the proportion of some glyphs, there started to appear inconsistencies between what I saw in Glyphs and what happens when using typography on the Web.

Both images show the font at: width=350 and weight=350



Here you have the file:
RSTReactorSansVF.ttf (11.1 KB)

Is this a bug? I tried a lot of different stuff the last two weeks.

Hope you can help me.

You exercise the most control if you have a rectangular master setup. For brace layers, run the mekkablue script Interpolation > Add Missing Brace Layers.

I would not add more layers. You have too many already. Make sure you have all masters in the middle at wght 400 (and not 416).

I’ve tried both solutions and everything seems to work fine.
Now, I have two options to solve the problem. Thanks!