stdavailablecapacityisvalid field cannot be cleared for First Interval in Work center.

[tincy-01]

Hi All,
I am currently working on developing work center module using SAP Core Data Services(CDS).I am referring the API document by SAP.
https://api.sap.com/api/OP_WORKCENTER_0001/path/post_WorkCenterCapacity__WorkCenterInternalID___Work...

I am facing some difficulties on Interval and Shifts section there.

As you know, we are having Create, Copy, Change Operations. 
For create operation, there is no issue in interval and shifts. 
If am trying to Copy from an existing work center, in intervals section, am getting an error like:

"stdavailablecapacityisvalid field cannot be cleared for First Interval",

My payload structure for _Interval is as follows: