I'm now 99.9% sure I know perzactly what's causing my occasional Duenna error. It's the Radio/CD gauge. Or better said, it's when I go to change CD's in it. My comp goes to read the CD and locks up FS for about 20 seconds or so. This time I had the Duenna pulled up and watched it as I put the new CD in. FS stopped then the Duenna flashed red for a couple of seconds.
Anyway, I should be showing an error now just after the 14 minute mark into my flight.