Duplicate Time Card Entries

Summary

Duplicate Time Card Entries are loaded through REST API

Content

Problem Description 
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We are using the hcmRestApi/resources/latest/timeRecordEventRequests API to load the time card details. We followed the below steps to load the time card:

1) Called the REST API via SOA as ADD operation 
2) The load was successful 
3) Ran the "Process Imported Time entries " in HCM 
4) Called the Rest API via SOA as UPDATE operation 
5) Ran the "Process Imported Time entries " in HCM  
Found duplicate Time Card entries after step 5.

Can someone please help me out in understanding why it is creating new entries even though after sending Operation as Update.