Strange kerning interpolation (bug?)

I’ve made a A.ss01 glyph, that is in the kerning group with A. In the regular, it follows this group, wheras in the XBold, I created a kerning exception for some cases involving A.ss01 T (just an example). I thought this would work fine, but the kerning values I get in InDesign don’t make any sense. They are, from Regular to XBold: -85, -30, -64, -100. So, the interpolated instances are interpolated from a regular with kerning value 0, but the regular itself is fine.

Any idea whats going on?

InDesign’s kerning values are normalised for 1000 UPM. Which UPM does your font have?

I’ve never dared to tinker with the upm, so 1000.

The regular instance is not interpolated. So it ignores the exception in the other master and sticks to the class value.

Yes, I know. The Regular is fine, but the problem is in the semibold and bold:

Regular -85, SemiBold: -30, Bold: -64, ExtraBold: -100

The values in Bold are wrong, and they are NOT the class values.

to interpolate the kerning, it needs to assign values to all masters. I need to check why it is using zero instead of the class value. Can you send me the file?

Of course. It’s on its way!