Pro Forms + Jet Engine - create post with custom date field

I have a jetengine CPT called reservations, with custom “date field”.
I am creating a multi-step to create a new post of type reservations from the front-end.
I cannot manage to get the value of “date” field input in the form to be stored in the custom field on JetEngine. I tried all combinations of date, datetime, save as timsetamp option in jetengine, all in vain. The form is submitted ok, I find a record in the submissions, and a post is created successfully except missing that custom date field value.

Any ideas?
Thank you,