Dual write update not happening

Hi all,

I am trying to pass data from F&O to CE via dual write. I have created a custom entity and whenever I am creating a new record it flows into CE, however when updating the same record I am getting an error:

Unable to write data to entity ####.Writes to #### failed with error message Request failed with status code PreconditionFailed and CDS error code : 0x80060892 response message: A record that has the attribute values Field1, Field2 already exists. The entity key Field2 requires that this set of attributes contains unique values. Select unique values and try again...
Note: Field1 & Field2 are part of PK in F&O and CE also Field2 is a lookup in another table which is header. I have checked that data is flowing in CE and also all fields are mapped properly. Can anyone please advice me on how to resolve this issue.

Thanks in advance!