Duplicate derived date field after synchronizing scripted tables

[michelle22]

I have a query relating to synchronizing scripted tables in Data Manager. I am running a script in the Data Load Editor, which contains three tables (all containing a [Date] field) and an autoCalendar function, ending with the standard 

DERIVE FIELDS FROM FIELDS [Date] USING [autoCalendar] ; 

This loads fine when loading via the Data Load Editor; however, when running the load script via Data Manger and synchronizing scripted tables, this results in "Error: Duplicate Derived Field". On investigation in the load editor, a new auto-generated section has been created with an additional DERIVE statement, which is clearly causing the issue.

I understand that the solution is to load via the Data Load Editor, but can anyone explain why this occurs? I have read the documentation on synchronizing scripted tables, and have only found the following:

"If you remove or modify fields in data load editor, you must delete or redo any derived fields or associations in the synchronized table." 

Is it because the Data Manager/synchronized table is associating the common [Date] fields and then needs to derive them again? 

[Andrew_Delaney · Accepted solution]

The data manager is trying to be helpful and autogenerating some values for you, unfortunately this conflicts with your preexisting data load script.

Generally once you move into the Data Load Editor, it is not a good idea to go back to the data manager, because you do not want to recreate the autogenerated content.