Required fields in a tab not setting off error

Are you sure that the “save and close” button is really trying to save the models on the underlying tabs?  I suspect that you are only saving the data on the first page and not trying to save data shown on the other tab. 

There is 1 model for all the fields.

Should there be an error when a tab has unfilled required field?

Yes there should be.  Can you post a screenshot of one of the tabs where the required fields are,  and a screenshot of the required fields properties in the builder? 

Thanks.