Nik, If the Media Zones are working from the 'Emulator', have you tried re-downloading the project into the NevoSL and then doing a soft reset? The only other thing that would cause this from the NevoSL's side, is if there is a low signal strength/TX rate (Settings/Wi-Fi/Advanced/Status).
"Until you bring a remote home that will put the kids to bed, I'm NOT impressed." My lovely but technophobic wife