I'm having a very strange network issue with my Denon AVR-X2200W receiver when using Spotify connect.

The situation: I stream music on the receiver using Spotify connect. When my phone (OnePlus 5, Android) wakes up from standby, i.e. when I unlock it, the music stops and the receiver has a network error. Sometimes there is a noise (like white noise) just before it stops. The receiver then goes into network restart mode and after it comes back online I can start playback again.

I have tried assigning static IPs to both the receiver and the phone, but this doesn't fix the problem. Neither does setting all the port forwarding settings up for Spotify connect as recommended by Denon. Other devices on the network (including my old iPhone) don't cause any issues.

Any suggestions on how to solve this prolem?