I recently upgraded to Kodi 19 via OSMC on my rasbperry pi 3. For some movies with 5.1 audio, the sound was not working anymore and the video was lagging/slow.
In the logs I could find errors such as:
[drm:vc4_hdmi_audio_prepare [vc4]] ERROR Not able to map channels to speakers (-22)
ERROR : CActiveAESink::OpenSink - no sink was returned
I just spend one hour trying different settings but it turns out it was just the System / Audio / Number of channels → Set it back to 2.0 that did the trick.
I hope it can help others!