I am using MS documentation mentioned at "https://developer.microsoft.com/en-us/graph/docs/api-reference/beta/api/listitem_update".
All other types of fields are getting updated but user and taxonomy fields always fail.
Please note that I have also tried to give same json item for user/taxonomy field for update which comes out after any other successful update request.
For Example: all of the below listed attempts failed.
PATCH https://graph.microsoft.com/beta/sites/{site-id}/lists/{list-id}/items/{item-id}/fields Content-Type: application/json
{ "Color": "Fuchsia", "Quantity": 934, "Owner1": "Himanshu Pandey",//this fails "Owner2": "Himanshu Pandey|(guid for User)",//this fails "Department1": "Human Resource", //this fails "Department2": "Human Resource|(guid for human resource item)",//this fails }