I bought an EZ-Robot kit at Maker Faire last weekend but have been having all manner of trouble getting it to work reliably (difficulty making & maintaining Bluetooth connections, servos chattering under no load/heatsinks getting hot, random board resets & brownouts). I finally figured I might have a faulty board when the HC-SR04 sensor I wired up started smoking. Upon testing, I found that I was getting the full supply voltage (i.e., whatever I was supplying to the power plug) at all the '5v' outs from the board. The 3.3v pin is fine. It makes no difference if I use a 9v battery pack or 12v external PSU, whatever I put in, I get out from the 5v lines.
Is there anything else I should look for before I open an RMA ticket?