Hello Gunther, Thank you very much for reminding me of your response.
I’ve pasted my reply from May 3 below, in case it was missed. From my 
perspective, that should address the issue - please let me know if you
see it differently.

At the time I was busy with many things, and forgot about it.
I use the O'Reilly XQuery book when programming XQuery, which does not yet include the $options parameter. This shows me that I should use the BaseX documentation instead.

Using the right options, as you suggest, indeed fixes the 'problem'. Thanks again!

Best regards,
Nico