Hi Bob,
Thanks for the update. I am glad to hear that you managed to get rid of the dropouts. Having a HDMI device plugged into the HDMI output of the VanityPRO would cause the video EDID from this device being combined with the audio EDID of the VanityPRO. I appreciate this may cause some conflicts in case of more complex HDMI chains with many devices. At least you have nailed it and I am happy that it works for you as expected.
Best Regards,
Pavel