Unexpected results when test-querying the authors of a publication

[laurianvm]

I've executed following query: to get a dataframe with all authors of all publications:

But when filtering to a specific publication (e.g. pub 352515 in this case - which has 3 authors listed in the ttl-file), information is sparse and appears to be listed multiple times:

Am I overlooking something in the query itself?

[laurianvm]

works like a charm when removing the nested OPTIONAL