[Events Manager] custom fields issue

I’ve just moved Events Manager plugin in the production environment and started to have an issue with custom fields.

When I add a new event, I need to define some custom fields for it.
I select a custom field, insert a value and click on “add custom field” button. As soon as I click such button, a URL call is triggered, my event is saved in draft and I jump in a new event (all fieds I previously entered are blank) and I get the error:
“
Your’s details are incorrect and cannot be published, please correct these errors first:
Dates must have correct formatting. Please use the date picker provided.
“

I even tried to insert event date and time before clicking add custom field button, but nothing changed.
If instead I first publish the event without custom fields and then I add them modifying the event, it works.

Such issue is not present in the development environment.

Last, when I go to new event page on WP admin, I see there is an error on the page:
Expected object:
post-new.php line:884
Property or method not supported by object:
load-scripts.php line:45
code:0 character:5598
URI: …

Thanks for your help