Hi @andreadelriva
I think we've found the issue. Braam, our developer, reports:
Managed to reproduce this by trying to submit the form before successful recaptcha response. So the submit button is now disabled until recaptcha response is received.
https://github.com/siteorigin/so-widgets-bundle/commit/e1f945223f0ac6a22523550e53f43cccf3d70aa8
This fix will be included in the next update of the Widgets Bundle. Perhaps we can run a quick test on your form once that update is released. Most likely in a couple of weeks time.
Thanks