While a field is hidden and the field is set to required you can not save.
The whole purpose of conditionally hiding a field is lost if the user has to take an action to find the hidden field just to make the selection so they form can save the form. If you make the field not required then you loose the ability to capture the data you need from the user.
Note: I have metaboxes in tabs and groups.
This needs to be addressed ASAP.