I just got the C200, and the issue occurs for me too, I get up and walk away and when I return to my desk the device has no volume. I tried changing cables, updating firmware, even changing the driver to "Always on" using the XMOS settings. I tried all my headphones and IEMS, nothing seemed to solve it. I could even recreate the issue every single time. Bummer, I like the device, but before I return it I figured I should ask if someone could solve it.
Also, I don't know which unit to go for if not this, I've tried the zen dac, fiio k7 and c200. I liked the c200 the most.