Hi Matthew,
Thank you for your post. To try and resolve the issue, go into the expression that is causing the error, add a space at the very end of the expression and press enter. This will recalculate the expression and may fix the error.
Since the cause of the error message is not immediately apparent, if you don't mind, can you please send a copy of the LEAP file for us to review? To do so, go to "Area: Backup" to create a backup LEAP file and save it to your computer. Then either reply to this message and attach the file or send it via email to leap@sei-us.org. We'd like to look into the error to prevent this issue from occurring in the future.
Thanks!
Emily