im not sure if this is the exact same issue or if it could be related, but i’ve noticed on some fonts i have now get a similar error and i can no longer export TTF/OTF
what they have in common is that they don’t have “ “ (space)
(reason they dont have spaces is that they’re “components”, glyphs later to be merged into a larger singular font, rather than being proper fonts)
i can easily workaround this by just appending a space though
i can see the error being thrown in Vivaldi’s and Firefox’s console (when i append then remove the space), though i don’t really know what’s going on 😅