I checked the cable four times, cut it, soldered it new. Always the same problem. And how it could be a cable problem if it only appears with audio via WiFi or Ethernet? Bluetooth over I2S works fine. Also if I use 3,5mm jack connector. If it would be a cable issue, also this signal should be distorted. And how can It switch from left to right depending the LRCLK setting? If I use the Mono mode in the App and use only left channel it works fine. If I use Mono mode for right channel, distorted signal appears on both speakers.
If I use the SPDIF connector also it works fine, but I think it uses the additional extra pin.
I use an exclusive power connection with 5V which can deliver up to 5A via the separate power connector.