Not able to set returnValue Object Keys

[MarkDM]

I receive the following error when trying to return an object from AppScript
Failed App Script type translation: Key 'Output' not found in returned object.

However my ReturnValue type in the automation is "Object".

This means I should be using the [StepName].[Key] format.
None of my keys are being found.
If I add the "Output" key in my returned object from AppScript then it finds it, but only the value from the "Output" key is available.

I return an object that looks like the following from AppScript...

let myObject = {"myKey1": "1", "myKey2" : "2", "Output" : "Not What I want" };

return myObject;

Then in my Automation I set the returnValue as an Object.
I setup 3 Keys.
myKey1 : LongText
myKey2: LongText
Output: Text

Then In my Data Action task, I set my columns
myColumn1 = [StepName].[myKey1]
myColumn2 = [StepName].[myKey2]

But this assigns only 1 of those columns with the value "Not What I want" and the other blank.

Removing the Output Key and definition causes nothing to be updated and the error to occur again.