Originally Posted by LarryJ

Unscheduled MCAS presents as a runaway stabilizer and the existing runaway stabilizer procedure is how it should be handled. The longer you delay applying the appropriate procedure(s), the farther the stabilizer runaway (regardless of cause) progresses and the more difficult it will be to recover. A stabilizer runaway event is not the time to delay while considering the possible causes. The first items on the checklist are called "Immediate Action Items" for a reason. They need to be accomplished promptly to prevent the situation from deteriorating further.