We have tested your issue with the following sample code using the latest version and found the issue as per your description. Output file gets corrupt after executing DataLabels.setPosition() method.
We have logged this issue in our database for investigation. We will look into it and fix this issue. Once, the issue is resolved or we have some other update for you, we will let you know asap.
This issue has been logged as
CELLSJAVA-42112 - Output file gets corrupt after executing DataLabels.setPosition() method
I have also attached the output excel file and the screenshot showing the corruption of the output file for a reference.