Fet driver failures apparently can also damage the driver chips, resistors and capacitors. These should be replaced also, but unless you are very handy with SMD components and a fat tip soldering iron i'd suggest speaking with Vems HQ about a repair.
Poor ground can cause all sorts of issues.
My self built box suffered repeated FET failures and I ended up using IGTB's instead. When the FETS in my box died they died dead short to ground. I put my problems down to my self build box more than anything else though.