After adding the compute node to the stack, it looks like it is trying to create a new trait "COMPUTE_NODE" in placement but since it does not start with the prefix "CUSTOM_" it is throwing an error, at least to what it appears. Connecting to the api throws the same error when "CUSTOM_" is not prefixed to the trait name.

2020-01-01 10:11:54.873 108768 ERROR nova.compute.manager nova.exception.TraitCreationFailed: Failed to create trait COMPUTE_NODE: {"errors": [{"status": 400, "request_id": "req-3d0d8529-91aa-463c-92f0-c30c102aa414", "detail": "The server could not comply with the request since it is either malformed or otherwise incorrect.\n\n The trait is invalid. A valid trait must be no longer than 255 characters, start with the prefix \"CUSTOM_\" and use following characters: \"A\"-\"Z\", \"0\"-\"9\" and \"_\" ", "title": "Bad Request"}]}