It is not 100% fixed, but I can confirm that I have certain .blend files with audio tracks in them that submit properly now in 2.81. I am not sure why some others don't submit to Flamenco, but there is the easy workaround of deleting the audio track before submitting the render or turning on "Relative paths only" in the Cloud plugin settings.
Nov 26 2019
Unfortunately I won't have time to do this, but on a positive note I am unable to replicate this issue in Blender 2.81 with latest Blender Cloud plugin.
Oct 2 2019
I have discovered that the error during the job submission can be prevented if "Relative paths only" is turned on in the Blender Cloud settings. I am not sure if that will introduce other issues, or if this is on by default, but it appears that it addresses the issue.
Sep 24 2019
Error is still occurring for both 2.79 and 2.80, but only when a WAV file is in the video sequencer and I try to submit to Flamenco. The .blend files don't submit and get an error as below, with the display in the Flamenco Render tab reading "Found asset Narration-Audio.wav" when it stops packing. All files submit properly once the audio track has been removed, which is an acceptable workaround for me.
Jun 14 2019
D:/ is a local physical data drive on my main Win 10 workstation.
R:/ is the Flamenco project.
R:/ is a network mapped folder location to D:/Flamenco, so in the case of submitting the job, R:/ points to the same hard drive. R:/ was created using Windows "Map network drive", which I don't believe allows you to specify a protocol.
All Flamenco workers have an R:/ mapped back to my workstation, which is also running Flamenco manager.
Inside R:/ are three folders:
Jun 13 2019
I have been able to successfully submit to Flamenco a version of the file that has the object with an Ocean modifier, but only when the Cache path for that modifier was empty.
Jun 12 2019
Adding a sound file to the sequencer in an empty .blend file was enough to reproduce the error for me, but I am attaching this actual file. This file has the proprietary elements removed, including the WAV file in the sequencer. To get this to submit to Flamenco without error, I have to delete the WAV audio and both the Alembic fluid surface and the Ocean modifier fluid surface.
Jun 11 2019
Which version of the Blender Cloud add-on was used?