Is the unit mounted in an aircraft or loose to investigate at home?
Have you tried running the unit with the SDR disconnected?
If you plug a laptop into the Ethernet port and navigate to 192.168.1.1 can you see the status page? (This may not actually work - a PAW person will need to check this as viable)
On the status page, you will be able to see PSU warnings and the status of the Wifi.
AIUI, Wifi on the Rosetta is on the main Pi board, the Wifi dongle is for iGrid.
I have used a USB voltmeter to troubleshoot SDR problems - it will tell you what the current drain is and if the voltage supplied has dropped in the USB ports due to PSU problems...
