I am having an issue where cases are rerouted through omni channel when assigned to queue member. example: I have 3 queues configured in omni, when a case is assigned to 4th queue it is dropping of from queue backlog which is good but if i assign to any of the queue member from 4th queue it is re routing through omni again.
I would say that is happening because it once was a Work item, so in your changing its owner to another queue Omni considered it assigned still (as this queue does not have a Routing Configuration assigned, it acts as a User); then when you assigned it to another user, maybe their Presence status was Offline or Busy, and so it tries to route it again.
This assumes you are talking about a Case that was at one point routed in Omni, Ie. it became a Work item.
So I think that the solution would be to delete the AgentWork record. (this is mentioned in Sf help material as an option: "This object is never automatically deleted, but you can manually delete it when the State field is in a non-active state.")
Or, to not let the Case enter Omni in the first place.
I hope that gives you some ideas?