FDM Import Fish cannot turn yellow and prompt "Import Fail" Error

Hi

I am using import script to import data to FDM.

However, after I click "Import" button, data appears in FDM and correct.

But I still get "Import Fail" Error prompted and the import fish cannot turn yellow.

For the import script, I have added the return value "script_name" = True.

And I output this value to the log file and can see the value is True.

Can anybody let me know how FDM judge the import is success or not?

Thanks.

James