Virb Edit can't render if source video started recording with external audio cable

I've had a strange issue where if I use video that was recorded from the beginning with the external audio cable connected, Virb Edit will fail with a 'video error' when you try to produce a movie. It does not matter where the clip is in the video or what the audio source is - cockpit connector, external mic or just the connector cable itself. In edit mode, there is no indication of a problem: you can edit, move and playback everything with no problem, but when you select export or post to FB, and the rendering process begins, you get an error pop-up as soon as the process hits the offending video clip.

Now, if I start the recording without the cable out and THEN plug the external connector in AFTER the recording starts, it works fine (a real pain if you're trying to set up multiple shots). This is true even if you trim the first part of the video off when you edit the clip.

Has anyone else seen this problem?

Don't have an audiocable so can't test it.
But with clips from other sources the audio level has to be set to 0, otherwise VE will not export.
It's not much use to you, but could you try setting the audio level to 0 and see if VE will export.
This will provide the developers some clues whether the problem lies in the same direction.