I just wanted you to make sure that the new page was being published to the same location as the old page. You can check that in the inspector window, first tab where you enter the Folder and Pagename. You can ignore that if you want back to the old page.
Anyway, I just tried your form and like @LaPan I did not get any error message. The form appears to send fine. Safari 11.11.1
Well, I’m still not sure what you are talking about and I’m not receiving emails from you.