Interpolation / kerning errors

I'm making a 2-axis variable font. I can generate through fontmake without error, but I'm seeing some strange things when I proof in Illustrator / Photoshop 2018.

There are kerning pairs that have no basis in the masters. In this example **.N** is -50 and **OT** is -110. In the masters these values are both 0.

There are lots of interpolation errors that show up at seemingly random places as you drag through the width and weight options. I don't see the same interpolation errors when I proof in FontView.

I'm attaching my designspace doc for reference (saved as .txt). I'm new to this so I'm sure there are some things wrong, but I wanted to report in case these are actual errors in fontmake.

Thanks in advance!

[CHOP-Variable_ALL.txt](https://github.com/googlei18n/fontview/files/1459644/CHOP-Variable_ALL.txt)