JsReport not rendering docxCheckbox – Docker

I have a Docker Image where jsReport is rendering a custom doxc file to a pdf. I have normal string values like firstname and lastname + some checkboxes depending on previous user input.

Evening works fine for the string values, but the checkboxes will not get rendered.

After rendering, it looks like this:

The data looks like this:
{
"customer": {
"fullName": "John Doe",
"birthDate": "10.10.1999",
"companyRegistrationNumber": " / AB123456",
"fullAddress": "Street 1234 B5",
"email": "[email protected]"
},
"date": "11.09.2022",
"ready": true
}

It is rendering something, it even uses the "ready" value because it displays the same string as "true", but it is not displaying a checkbox