[Defender] Defender issue

This site uses a YMM(Year Make Model) plugin, and it creates a search widget on the sidebar. (e.g https://rolloface.com/product-category/big-brake-kits/)

Issue:
The "search filter" suppose to be an AJAX action, which you select the Make, then you would be able to select Model, and then the Year. But once I activate all functions from "Defender", the "search filter" doesn't work anymore, you would have to select the Model, then click search button, then choose Make, and search button, then Year.

I first assuming its caused by hummingbird plugin, but suprisely its caused by "Defender" after troubleshooting, I just don't know which part of the defender caused it.

PS: deactivate the plugin doesn't solve the issue, I had to do a full cPanel restore, and not activate any defender function.

Please assist me to find out which part of Defender caused issue, and how to bypass if. (I have cPanel backup, so you can troubleshoot anyhow you want)