k8s swagger: https://raw.githubusercontent.com/kubernetes-client/javascript/master/src/gen/swagger.json
What operation the command kubectl label service service1 --overwrite x=3 uses?
I can't find it.
Try running your command with "--v=8" which will show you the complete request and response to API server.
Example: kubectl label service service1 --overwrite x=3 --v=8