@elmando: Please can you try heading to Settings > Battery and device care > Optimise now, followed by Memory > Clean now. Also, if applicable, tap the Recents button in your Navigation Bar and close down any applications that aren't in use by swiping upwards on the preview windows of the apps. If the problem persists, try checking Settings > Sounds and vibration > Separate app sound, and toggle it off if it's active.
