Hi @kirbypoh
I’ve had the time to investigate this issue further but could not identify an issue with the Popups for Divi plugin: The dropdown lists in a contact-form popup on a fresh site with WP 5.1 and Divi 3.18.19 did work great in Firefox, Safari, and Chrome.
However, I’ve made a few changes in the plugin which improves the javascript event handling and might fix the issue for you (as a side effect).
I suppose there might be a problem with a different plugin on your website. Maybe even caused by WP Fastest Cache – I’ve seen this on other websites (not with WP FC) that a JS file was included twice in the minified JS file, or that the individual files were in wrong order inside the minified JS file and because of this some event handlers were attached multiple times to the same DOM element.
My tip: Try to update to 1.3.0 (coming in the next few days) and then disable WP Fastest Cache for a test and see if everything works. When it’s still not working, then possibly a different plugin or theme JS causes a conflict.
Philipp