Plugin conflict

I’ve narrowed plugin conflict to Conditional Discounts for WooCommerce (eg. when I disable this plugin the error ceases…

Would there be any obvious reason that when editing functions.php via WordPress themes editor that the following error displays after 30 seconds or so:

“Something went wrong. Your change may not have been saved. Please try again. There is also a chance that you may need to manually fix and upload the file over http://FTP.”