Dedeploy standard edition SfB front end server fails

Hi.

I've upgraded a customer from a Skype for Business standard edition server to an enterprise pool.

This is all jolly good and working but i canot delete the redundant standard edition server from the topology.

The error log reports you have to check that it does not host any services or users. I've run all the checks and the only thing running on it is the audio test service. 

No users are homed on the pool

no conference directories

no applications or endpoints and so on.

The audio test service cannot be removed by any powershell so I've even tried removing it in ADSIedit but still with no luck.

 Anyone experienced the same issue and hopefully the solution?