Sum duplicate rows from Rest API export data slice to move data to FCCS through import data slice

Summary:

Trying to move data between Planning and FCCS through Rest API export/import data slice using a groovy map but getting duplicate lines that aren't adding together on load even with aggregateEssbaseData turned to true.

Content (required):

I have written a groovy script to export data out of Planning through Rest API, modify that data through a groovy map and then import that data into FCCS. My initial script worked great, data flowed through from planning to FCCS but the issue was that part of the data were not correct due to my mapping creating duplicate lines. I have "aggregateEssbaseData" turned to true but seems like that only works for data that is existing within FCCS, not the incremental data being loaded, it just takes the last row on the load even though there are