Registered an account here just because this thread solved months' worth of frustration. I have the 2i MDC in my C368 primarily for streaming music, and it's been a nightmare getting it to stay linked to my network and to Spotify Connect. NAD's support just reiterates the same "reboot it" then "it's Spotify's fault" every time I've sent in error logs.
If you're reading this in the future and the Wi-Fi is giving you grief, find any way to get an ethernet cable in your 2i MDC possible. I took an old router and set up a wireless ethernet bridge in 5 minutes, and now it works flawlessly. Most modern WiFi networks are centered around 5GHz, and even when I'd force my phone to get on the same 2.4GHz channel as the 2i's WiFi dongle, I'd would still experience frequent disconnects and drops, or sync issues between what Spotify was supposed to be playing vs. what the MDC was playing.
I'm not thrilled this $500 product has such a cheap WiFi dongle that doesn't support 5GHz, but after hours of troubleshooting, configuring router settings, and turning receivers and routers off and on dozens of times, save yourself the headache and get a WiFi ethernet bridge if you can't hardwire it directly.