Hello,
i found out it is due to ambiguous citation. If i change the Name format in the ‘‘Include the authors initials or full name in citations’’ menu in ‘Citations’ → ‘Ambiguous Citations’ and update my bibliography the citation changes, e.g. to ‘(JW Ross & Feeny, 1999)’ or whatever i choose.
However , if i remove the checkbox for ‘Include the authors initials or full name in citations’ and update my bibliography the initals are still there. Why???