Logitech C920 causes sample rate = 0?

I have a bit of a weird problem.

A tester reports, that his Logitech C920 web cam causes our standalone plugin to quit directly after starting.

We did some debugging:
Whenever he sets the Logitech web cam as the audio input, the JUCE audio settings dialog reports that no sample rates are available.

Apparently the fallback sample rate is 0 in that case.
So in other words: using the Logitech web cam as an input causes the output sample rate to be 0.
And apparently a sample rate of 0 causes the app to quit immediately after starting.

Anyone else seen this?
The problem also appears, when I give the tester a default JUCE standalone plugin (without any of our own code).
I can see that the assert jassert (sampleRate > 0 && blockSize > 0); is hit lots of times, on line 107 of AudioProcessorPlayer::audioDeviceIOCallback.

The tester is on OSX Mojave, running a stand-alone version of our plugin.
We compile with JUCE v6.0.4.