The temporary fix is "use a font smaller than 60KB" 
This is only true for a part of the users.
There's no font below 60kB which supports e.g. CJK. Those users don't have the choice to switch to a smaller font (seeing only square boxes is not an alternativ).
The temporary fix in this case is to increment the font buffer as you proposed it in a comment in Flyspray and it was also proposed by another guy some years ago. I don't think he's still around, but anyway, thanks to that guy. His patch was a noticeable improvement for me.