- The specific mention of "cut off" in the CVR is very telling. If both pilots were genuinely surprised, you'd expect they'd say something like "engine failure" or "loss of thrust" first. Noone thinks the engines have been shut down as a knee-jerk reaction to a sudden loss of thrust.
- If investigators had the slightest indication there's a software or hardware bug out there that randomly causes dual engine failures, an emergency airworthiness directive would have been issued by now. This hasn't happened.