21R2 Error occurred while updating the PO Reference in the Manual Supplier Invoice Only for German Language

The issue has been resolved

After looking into the problem with the IFS Core Code, I found these code changes and provided a fix, which resolved the issue.

Summary:

Basically, before saving a PO reference, a validation method returns a response as a variable, and that variable has a different length,
And that response value that is greater than the variable length will receive this error message, and we advised the customer development team to set both variables to the same length and try to increase the value. 

So, after the customer development team made those changes, they confirmed that the issue was resolved.

(I've included the document that I sent to the customer, which contains all of the technical information.)

Thank you very much,
Shafraz