If you try and add an extra datasource, the report just prints multiple pages. (see attached pdf) jrxml-example.pdf (19.4 KB)
I discovered this as I am trying to add a chart in my personal app. It prints the report fine, but then adds numerous blank copies of the report as pages (the size of the chart dataset) afterward.
To show an example, I just tried adding extra datasources to the sample-library example app
Have attached templateBook availability in department.zip (25.5 KB)