Sidebearing formula misbehaving in recent Glyphs

I have a Glyphs file I was working on in Glyphs 1257, where I set up the RSB of the H as ==|-2. In Glyphs 1257, this gets correctly calculated as 14.

When I open the file in the current version (1274), the formula turns red and after clicking on the circle arrow, it becomes 16. Looks like that’s a bug that was introduced recently?