This is a Salesforce known limitation with deploying process builder. You cannot deploy a flow version that is currently active in the target org.
For example, if your target org has Process-4 which is currently active and you try to deploy the same version Process-4 from a source org. The above error will occur.
Clone the flow in the source org to a new version (Process-5) then deploy the new flow version to the target org. Remember to activate the new version in your target org since all flows are deployed as inactive by default.
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