Adding a text that has the unicode "\u000b" will throw an error when you open the saved docx.
I am using docx4j-JAXB-Internal 8.1.6. The same issues occurs with "\u000c" so I assumed it happens with all Control Characters. At the moment I am simply removing them with:
String removeControlCharacters = this.content.replaceAll("\\p{Cc}", "");
and then adding it a Text and it works fine.
I am wondering if anyone else has had this issue and what the best way to resolve it is.