Steps to reproduce the issue

Write article in joomla 3.9.23 frontend, with diferent fields assigned to diferent categories

enter data in field

then you select category which don't have that field assigned

and your field disapear

Expected result

First select category then enter data in that category assigned field

Actual result

First enter data in field, then select category, if selected category don't have that field, you get other field that assigned to selected category and you need to enter data in that new field

System information (as much as possible)

joomla 3.9.23

Additional comments

Maybe first tab should be publishing with selecting category that way you will not get to select the field which will disapear then you select category?