Hi @massimoantinoro,
Were you able to replicate this issue yourself by submitting the form yourself or you just saw it from the stats?
Could you perform a conflict test by disabling your other plugins and switching to default WP theme to see if the issue happens there as well? Also make sure that the caching is disabled.
If the issue is gone, enable them back one by until the issue is back and that should tell us where the issue is coming from so we can debug it further from there.
I suggest doing this on a staging site or if you don’t have one make sure to have a backup of your site before doing the test on a live installation.
Cheers,
Predrag
Thank you for using Hustle. We are going to close this ticket for now because we have not heard from you in a while. If you still need support we can reopen the thread.
Cheers,
Predrag