List managed devices, combination of filters devicename and userdisplayname only returns devicename results

[wkesteloo-ydentic]

I'm trying to get a list of managed devices

A single filter on devicename returns te correct results https://graph.microsoft.com/v1.0/deviceManagement/managedDevices?$filter=startsWith(deviceName,'D')

A single filter on userdisplayName returns results

But the combination of the 2 filter only return the devicename filters. https://graph.microsoft.com/v1.0/deviceManagement/managedDevices?$filter=startsWith(deviceName,'r') or startsWith(userDisplayName,'E')

Is there a restricting of using both filters? or is there a problem in the api?