Bug when incorrect fields

Hello,
I have a problem with the form when some fields are not correct. When I click on send I get the message asking to correct the mistakes on the fields but at the same time the “sending turning wheel” (sorry I don’t know how to call that) appears as if the message is really being sent, and it is never stopping…
2 or 3 months ago this was working perfectly.
Any idea of how to correct this?
I gave the link to the page, click on “send an inquiry” for test.
Thank you.

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