How to remove orphaned duplicate devices

Hi,

I'm having a bit of a problem with some duplicate devices, who seem to be orphaned. But I cannot delete them.

The most likely cause I could think of is a wonky sync with MECM in the past. 

The question for now is how can I delete the duplicate?

Here is a example:

The problem is with the device managed by ConfigMgr, when I open this device I see:

So, no delete button or AAD device ID, only a Intune device ID. How can I delete this device from Intune?

Greetings Harald