Apps Script return value is empty

[pro100bear]

Hello,

I am developing an app that checks shipment tracking statuses. I have a table containing tracking numbers, and every day, an Apps Script is supposed to run and send these tracking numbers to Ship24.com via API. The possible response statuses are: delivered, out_for_delivery, etc.

My bot:

Event occurs: daily
For Each Row In Table: yes.

Process: call a script.
Return value: yes.

Sample of one of the return values:
{"Success":true,"ReturnValue":"{ \"stringValue\": \"delivered\" }","Task Type":"AppsScript","Task Name":"Task for script","ScriptId":"1liNoLPokoBdqdxtTyR9utmTQnBr_F-jYV_vz_e0pTLMdo52vcJZekeZu","FunctionName":"getTrackingStatus","FunctionArguments":"{ \"stringValue\": \"9434611105503870######\" }"}

Next step is to create a new record in tracking_history table.
Column "tracking_id_ref" = [tr_id]
Column "event" = [script].[Output]

And here I get this error:
Error encountered in step with name [New step]: Error: Perform DataAction 'New step Action - 1' failed because Can't add or update a row because a required value is missing. Provide the required value and try again. Row ID to correct: 6IMBqqGYib4v6nbB0xWui0 Missing value in column: event Expected data type: Text Error: Perform DataAction 'New step Action - 1' failed because Can't add or update a row because a required value is missing. Provide the required value and try again.

What can it be?

Thank you.