I have the exact same problem after updating WP: AJAX ERROR. Website is using php 7.2, latest WP. I looked at the log file and did not see any error. Please explain how to fix it. Thanks!
This reply was modified 4 years, 11 months ago by tnv.
I did an extensive search and debugging to finally find the cause: mailchimp form intrusion on quforms. I had to delete mailchimp custom functions completely. That was it. Now, quforms is working well.
