Instance already error while creating join data source c4c sdk

hi all,

how to resolve this issue ?

Standard data source (Ticket ID as a key) and Custom Data source (ZID as a key )

we have made a node inside the SR and Custom Data Source is related to that custom node.

now, we want to join both data source( Standard Ticket & custom data source ) , while joining instance already error is coming.

Thanks in advance

Br,

iqbal