Error message when applying for a job

We’ve started to notice that users are getting an error message whenever they try to submit an application for a job. The applications are being received and the site is sending the notification emails.

You can see the error in this screenshot https://tinyurl.com/ylfdhhl9

There’s an error reported in the console

Unchecked runtime.lastError: A listener indicated an asynchronous response by returning true, but the message channel closed before a response was received

Could someone help us to debug this?

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