It seems as if this issue has occurred for about a week or so, but I am getting a Non-existent changeset UUID. when loading the customizer on my multisite site. The site is a subsite and is mapped using a domain name.
I have done some research and found that WP Super Cache is the culprit, and It hasn't been installed since October and have made sure that to my knowledge there is no left over files. I also checked the debugging log file and found nothing related to the error I am getting.
Thanks as usual.