I have created a new survey in production environment using Survey Force from the app exchange by Salesforce Labs. When the survey is sent with caseid and contactid links from a case using an Email Template built with the Survey Force link within it. The user receives the email and survey link, can access and fill in the answers to the survey, BUT, when they attempt to Submit the answers, this message appears on top of page.

Error: Some error occured while saving response

Does anyone know what is causing this, I've checked multiple threads, enabled headers, permissions are properly set, access and visibility seem to be exactly as stated in install guide. Our org is heavily customized and lots of code but I cannot find the source of the error. Thank you for your help and time.

Gabe