They are possibly sensitive to battery overvoltage fresh of the charge, or by being left in a charged state and then discharged in an abnormal fashion (ie accidental short while diagnosing faults etc).
I've had my DAs for over 2.5 years and I just found a quote in the manual last week; it says you are supposed to flip the prop over a couple times after flying to discharge the ignition box. Neat.
Not that it will help you now, but good to know.