Hello,
Thank you for providing us the details.
Based on our logs(per the X-Request-Id) and the provided JSON input, it looks like the actor reference is pointing to a patient that does not exist. Resulting in the 422 Unprocessable entity error.
Non-existent patients cannot be used as actors.
The existence of a patient can be verified by doing a read on the Patient ID.
https://fhir-open.sandboxcerner.com/dstu2/0b8a0111-e8e6-4c26-a91c-5069cbc6b1ca/Patient/3674128
Additional details on how to search/read or create a patient can be found here - fhir.cerner.com - Patient
Thanks,
Praneeth (Cerner)