400 Bad Request on Selective Deploy when trying to update App.

Hi 

According to the documentation

https://docs.microsoft.com/en-us/rest/api/power-bi/pipelines/selective-deploy

I should be able to update the App but whenever I try I get a 400 bad request,

This is the code snippet I am using inside my body of my request.

"updateAppSettings": {

"updateAppInTargetWorkspace": true

}

removing the updateAppSettings section results in a successful selective deployment.

If anyone else has got this to successfully work, it would be good to know how?

Regards

Charles