JSON Object deserialized in D365

I'm experiencing the same results in code and Postman.   To keep it simple in the body of a Postman I have a JSON array - let's say the array has (1) = "A" and (2) = "B".  In the X++ code it shows the data as (1) = "B" and (2) = "B".   The last entry is duplicated to all others entries.  The X++ code is expecting a list.  The X++ code was originally written to accept SOAP objects and they work as expected.

I have looked at the header body in Fiddler and it looks correct.   All array elements are unique.

If I look at the data members in the ScanWorkX_QueryBuildDataSource class, they are set to the values I would expect,  each element of the JSON array comes over.  

. 

 [AifCollectionTypeAttribute('_SWXQueryDataSources', Types::Class, classStr(ScanWorkX_QueryBuildDataSource))]//, SysEntryPointAttribute]
    public str ExecuteQuery(List _SWXQueryDataSources, boolean _crossCompany = false)
    {
    ....code
    }

Does the Web API need to be setup from a Service Group / Service perspective different than SOAP?

A single JSON array element comes across and is processed properly.

any assistance is appreciated.

Thanks

Duane