The problem is that you probably have older versions of Glyphs around. And QuickLook is picking the quicklook plugin from any of them. So even if I fix a problem with the plugin, the old broken ones are still causing this.
You can check what version of the plugin is currently used by running this command in the Terminal:
qlmanage -m
If you don’t need that old version any more, delete it and run:
qlmanage -r
to reset quicklook.
Then run the first command again to see what version is used now. Repeat the steps until a good version is picked up.
If you can’t delete a version, you might be able to hide it by putting it in a folder (inside the Applications folder) and add that folder to the “Privacy” list in System Preferences > Spotlight settings.