Hello @Hannes_Moser,
Apologies for the delay in getting back to you here, @beka flagged us down but it looks like you posted in the wrong section, if you need technical assistance it’s always best to post in #support as that is the only section regularly monitored by support staff.
As for the primary issue at hand, can you try to reinstall the Roon Android App from the Play Store? Can you confirm if any other Roon Remotes are exhibiting these issues or is it just the Android 6 one with the issues?
Also, what is your Core / Network / Setup info? This info will allow us to better understand the issue: