KEEP_MERGEFIELD isn't keeping the mergefield?

[Mieges]

Hello folks! :)
I have the following problem:
For example, I would like to generate a docx for an event that contains all the surnames of people on my map. This should represent a list of invited guests.
I have taken the list with the two people from the example file FieldMailMerge.java. I have a Word template with a single mail merge field called “Kundenname”.

Then I call the following:

org.docx4j.model.fields.merge.MailMerger.setMERGEFIELDInOutput(MailMerger.OutputField.KEEP_MERGEFIELD);
WordprocessingMLPackage output = org.docx4j.model.fields.merge.MailMerger.getConsolidatedResultCrude(wordPackage, data);
String outputPath = System.getProperty(“user.dir”) + “/DOCX_from_merge.docx”;
output.save(new java.io.File(outputPath) );

Now only one name of two has been inserted.
The merge field is gone and I can't make another substitution to insert another name.

The way I see it, KEEP_MERGEFIELD does not keep the mergefield, right?

Or is my choice of method not appropriate for my project and is there perhaps a better alternative to output all names of persons with a single mergefield?

I am using version 8.3.13, Windows 11, Java version: Azul Zulu 1.8.0_432.

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