AEP 9.1 and Apache POI: freeze pane

Hi all,

I have an Excel file that I was editing in PP 8.5 through a Dynamic Java Component.

We now moved to AEP 9.1 and everything still work except the following instruction:

Sheet sheet.createFreezePane(0,1);

It gives the following message when opening the file: "Excel found unreadable content in ...".

Do you know what could be the reason?

Thanks

Florent