Our Rest API is deployed into PCF and there are 4 instances. We are observing below issue,

If one user is hitting the API 1000 times with the same input and at the SAME TIME if another user is hitting the API 500 times with different input, the second user is getting expected response for all 500 requests...but the first user is getting expected response for 999 or 998 requests and receiving second user response for one or two requests (mismatch).

Is this the case - one of the instances behind the load balancer is not responding to the updated change in one or two requests?