When you modified the extension did you give it a different name in the extension.xml and the .ext filename?
If you didn't use different names, can you check with the player who was having the issues and see if they have the unmodified extension installed?
I think that if they had a copy of the unmodified extension that it may have been using that and elvish and orcish would not have matched with fonts in base extension.
Just as an FYI - If you modify an extension from the base release, it's best to give it a different name so that players will download your updated extension rather than using the original extension if the names are the same.

