Titles appearing as gibberish

Opening a (large) library I was dismayed to find that most of the titles in a particular project had been replaced by gibberish.

Looking at the inspector, the correct text is still there and the font is now Helvetica Regular, but as you can see by the attached screen shot, weird characters are being displayed instead. The original font was Exo and that was always available on my system.

If I change the font (anything about it), it displays the correct text again. But this means adjusting the font of all titles manually and that will be a lot of work.

So I was just wondering if anyone knows what could have caused this.

Exo is a third party font, it did not come with your system. I suspect you have a bad copy of that font. Remove it from your system.

Hi Ben,
Thanks for your reply.
You are correct that Exo is a third-party font, I meant that it was always available on my system since I made the titles in the project. I know that FCP can replace a missing font with default fonts sometimes, but I have never encountered it changing the actual text/characters like this.
Removing Exo is not an option as I have to use that specific font for the client.I had FontBook validate the font and it found no errors.

If I change the title font back to Exo it also displays correctly again. I'm not sure for how long though

I'd remove the font and reinstall to be safe. But delete FCP pref files and the Library's render files, first.