Hello Friend,
Referring to "In the backend changes the url from server1 to server2, but auto-correlation cannot distinguish between session-ids that have the same name and different value" can you please give more details on this, like example value you got, generation logs for the value etc.,
"We tried manual correlation for those parameters that fail, but then it cannot find the returned session-id at all." if you are 100% sure you are giving the correct boundaries, placed the function in correct place and the value you are trying is in response(not in request). then the you shoud get the value u are looking for. Still u are not getting the value, then it might not need to be changed.
PLease post the generation logs and function u have tried to captured the values.