Checking For Errors
For example, in the Google chrome browser, go to View > Developer > Developer Tools, and then click the “Console” tab when your developer tools window comes up. Errors will show in red.
This will hopefully where the script causing the issue is, whether it’s a custom script you’ve enqueued from your child theme, or a script from a plugin you have activated.
Check Your Plugins and Custom Scripts
But if you don’t have any error telling you where the problem is, you need to troubleshoot the classic way. Basically, you just need to temporarily remove custom scripts and deactivate plugins, one by one, until you the problem goes away on the frontend of your site. This will tell you where the issue is, at least.