[Koha] Not able to enter personal name (MARC tag 100)

Hello, I am trying the demo Koha server (staff interface) at http://academic-staff.demo.kohalibrary.com/ I tried to create a new MARC record by entering some data into several field boxes, but was not able to enter a title into tag 100 subfield a (Personal name). I was even not able to move the mouse cursor to that box. I then attempted to change the tag 100 of an existing record in the database, but still not succeeded. Is this a bug of the MARC editor? Thank you Angela