This might be the relevant commit, and most likely line 127 is where it goes wrong. Not sure what would have to change to solve both my problem and the issue it's referring to, or if that is even possible. For now I can use the hack that I render the font as size 32, but then scale it down by half. It's not great, but it works.
Edit: Okay maybe it's not that commit specifically. But anyway, I'll make an issue for it. Thanks for the reply.