Motion and FCP do not handle font-related problems well – corrupted font duplicates, corrupted font cache and other similar issues cause these apps to display errors.
You can resolve such issues using mInstaller: close Motion and FCP, open mInstaller and uninstall the product that you are working with. Next, go to mInstaller's Settings via the Cogwheel Menu, [Fix] the fonts, reboot your Mac, and install the previously removed product again.
NEXT STEP IF THE ABOVE FAILED
Open the Terminal.app (you'll find it in your Applications > Utilities folder), copy-paste the following command, and press Enter (be sure to type in your admin password when prompted):
sudo atsutil databases -remove
Once the command has been executed, restart your Mac.
Next, you'll need to delete the generated previews (only if you've got Background Render turned on - Final Cut can store a pre-render of the incorrectly displayed font) via the “File” > “Delete Generated Library Files” menu (see attached screenshot - link at the bottom) - after that, the issue should be gone. Here's the tutorial for clearing FCP render files