[Koha] Cannot keep changes in MARC framework for Authority MARC Framework: PERSO_NAME Framework

[Marc Nürnberger]

Dear all,

Somehow I seem to be unable to keep changes to the Personal Name 
authority's MARC Framework. I was trying to the set the "repeatable" 
field to the 100 Tag (HEADING--PERSONAL NAME) by editing the MARC 
framework in Administration->Authority Types, but after submitting my 
changes to the field are gone. What am I doing wrong? (Working with 
Koha 3.00.00.107)

Appreciating any hints and suggestions,

Best regards,
Marc