Error Saving Upfront Theme Changes

I have been trying to save changes to my site in Upfront and I continuously get the error "There has been an error saving your changes."

I've gone as far as to upgrade all of my plugins, upgrade to Wordpress 4.5, and even disable all of my plugins. Each time I get this same result.

Currently I have my WP Construction plugin turned on, but when I was testing it was disabled.

Any ideas what might be going on? Are there any logs which might point me in the right direction?