Just to update:
Your revised file fancy_image_site file seems to have resolved the issue for us.
THANK YOU very much for your support.
If I could suggest to JOOMSHAPER, it may be time to add a designation within your customers profiles, if they are a PROVIDER or End User. This may help how you approach and support issues. I understand End User will ONLY have Browser access because 3rd party hosts thier site. The rest of us, have different infrastructure,security, mulit-site, multi-projects, access etc... Just like you ;-)
Either way, applying the Revised file seems to have resolved the Fancy Image Link addon for us...
Thank you again !