Hi 

When i  trying to update Lookup column using REST API, getting Error Below (Standerd Columns are Updating Fine)

{"error":{"code":"-1, Microsoft.SharePoint.Client.InvalidClientQueryException","message":{"lang":"en-US","value":"A 'PrimitiveValue' node with non-null value was found when trying to read the value of a navigation property; however, a 'StartArray' node, a 'StartObject' node, or a 'PrimitiveValue' node with null value was expected."}}} Bad Request

In the Workflow steps: im using Merge method and ín the lookup Value passing the ID of Lookup values 
am i doing right?