I'm suffering the same issue and I'm debugging it. While I haven't found the root cause, I've found that the issue is in cogl's glyph cache for Pango. You can use a debugger to clear this cache. I'm going to detail the steps here, but I should warn you that this is a bit of an expert option.
Preparation you need to do once to make the workaround work:
sudo apt-get install gdb gnome-shell-dbg libclutter-1.0-dbg libcogl-pango20-dbg
Then whenever you run into the issue, clear the font cache by running the following command line:
sudo gdb -p `pgrep -u $USER -x gnome-shell` <<<"print /r _cogl_pango_renderer_clear_glyph_cache((CoglPangoRenderer*)(_cogl_pango_font_map_get_priv(clutter_context_get_pango_fontmap())->renderer))"
This works splendidly for me, but I should warn you that if this command goes awry for any reason, it may hang your system. If that happens, a reboot is the only thing that fixes it.
I'm going to investigate further what, exactly, is wrong with the glyph cache, and open a bug report upstream.
Hope that helps!
Explanation of the command line: the part between backticks finds the process id for gnome-shell
. That is used to attach the debugger gdb
to the process; you need to be root (sudo
) to do that. The part between <<<"
and "
is the function call for clearing the glyph cache.
fc-cache --force --system --verbose
?