Bluetooth connection mutes after 10 minutes


there is a phenomen I need some help to eliminate.
Independent to the source (e.g. Fire TV stick or Smartphone) every time after approximately 10 minutes the tone mutes. When I press the pause button twice it is ok again and it runs without any further muting. I have installed the current version volumio on a RPv4.
Any ideas what can be the reason and how to solve the problem? Thanks a lot.