Unsupported audio format. Please set the audio output on your audio player to PCM
 

Laptop: Dell XPS 15 9500
Dock: Dell D3100
Monitor 1: Dell S2421HN via HDMi
Monitor 2: Dell S2421HN via Displayport (Sunix D2H13MD active DP 1.2 to HDMi 2.0 adapter)

Monitor connected to DP flashes, "Unsupported audio format. Please set the audio output on your audio player to Pulse-Code modulation (PCM) if available" when powered off and then on or when resuming from sleep.

No option on Intel or nVIDIA apps to disable HDMi Audio when connected to Dock. I don't have a USB-C to HDMi/DP adapter to try a direct connection. No hidden HDMi playback devices under sound control panel either.

If I disable the "Dell USB Audio" from the device manager the message no longer flashes but that's not a solution as I have my headset plugged into the dock.

I don't have the issue if I use both HDMi ports on the dock but then my monitors are restricted to 1080p/60Hz and I get random disconnects fairly often.

I'm able to run dual monitors at native 1080p/75hz with the HDMi and DP to HDMi adapter which seems more stable since I assume each output now has a dedicated chip (HDMi - DL-5911 and DP - DL-5915).

It seems that the DL-5915 chip used for the DP output does not support audio and is video only according to the DL-5910 product brief so I don't understand. Is it still passing an audio signal that the monitor cannot understand?

Is it possible to disable any audio signal over DP since it doesn't cater for audio anyway?

edit: I've also seen the below thread but there was no resolution.
https://displaylink.org/forum/showthread.php?t=63283