In the use case of Audio over UDP, end user intermittently cannot hear the sound of audio playback in an active ICA session, like dragging Windows sound volume bar, playing a audio file with Windows media player etc. until the session is disconnected and reconnected.

A race condition occurs in wfica32.exe audio processing threads. That results in the audio playback thread cannot be created to render the audio data transmitted from VDA side. 

To address the issue, please enable "Loss tolerant mode for audio" feature through the following Citrix policy settings.

• HDX Adaptive Transport: Preferred
• Loss tolerant mode for audio: Allowed

The article describes an audio data rendering issue in the "Audio over UDP" use case.

Refer to https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/multimedia/audio#loss-tolerant-mode-for-audio for more details about "Loss tolerant mode for audio" feature.