Cannot Submit Forms in Incognito/Private Browsing

We use Avada as our editor and theme where there is a Form Builder. The builder is used to build several forms, but there is one particular form where we have received notices that visitors continuously receive an error.

We disabled the reCAPTCHA in the form but it continued to return an error. After engaging Avada’s support, it was identified that the error would only occur if you were in private browsing/incognito mode which was rather unusual. This was caused by a caching issue – we were directed to disable the Security Optimizer and Speed Optimizer by Siteground.

Disabling the Speed Optimizer didn’t resolve the issue, but when the Security Optimizer was disabled, the form could be submitted without issues. When it is enabled, the form returns an error. Other forms don’t return this error, whether the plugin was enabled or disabled. Something within the form triggers the security optimizer to prevent the form from being submitted.

This was tested on Firefox 121.0 with cache cleared:

1. Enable the Security Optimizer
2. Open a private browsing session
3. Go to the site with the form
4. Submit the form – an error returns
5. Disable the Security Optimizer
6. Open a private browsing session
7. Go to the site with the form
8. Submit the form – it goes through successfully

The page I need help with: [log in to see the link]