Doing further research, I don't believe this is an issue with Page Builder at all. Wordpress sites are being targeted as well. I believe either AI Bots or reCaptcha farms are being used to defeat Google's reCaptcha. I looked at my reCaptcha dashboard, and the messages are not recording a score that would block them.
I have a number of sites I've developed, and only the sites with the Contact form as a root item in the main menu are being targeted. ie url/index.php/contact-us Other sites I've deveoped have the contact page in a sub-menu, eg url/index.php/about/contact-us are not being targeted.
I installed Clean Talk, and so far it is very successful as spam has stopped. It is a paid service, but so far, I am very happy with it. Especially given the number of brute force bots it is blocking. Here are the stats, so far it has only been installed for a few hours.
https://aera.asn.au/images/2024/08/Screenshot%20from%202024-08-22%2007-56-21.png