BP 6.5.1 - XDCR changes growing - "stream already exists for this vbucket"

It is a timing issue, could happen in a heavily loaded system with large number of buckets. The replication instantiation process tries to create a DCP stream for every vBucket by sending the create request and moves the state of the vBucket to INIT state. The response for the create request will set the state as ACTIVE and start processing the data. In certain condition thread which sets the INIT state can be preempted and executed after the response process. Though stream was created, the preempted thread can overwrite the ACTIVE state with INIT and lock the particular vBucket from streaming