SetEntityPermission removes existing UserGroup permissions

Hi Community,

I'm trying to set RunTimePermission for project entities using below code

let params = {
	allow: true /* BOOLEAN {"defaultValue":true} */,
	name: "UG2" /* STRING */,
	includeDependents: false /* BOOLEAN {"defaultValue":false} */,
	type: "Group" /* STRING */,
	projectName: "TestProject" /* PROJECTNAME */,
	tags: undefined /* TAGS */
};

// no return
Resources["EntityServices"].SetEntityPermission(params);

When we execute this service it removes existing UserGroup permission from entity.

Is this a bug or I'm doing something wrong here. 

TWX Version : 9.4.1

/VR