Saute!
Good questions Gordon.
The way FCeng described it on another thread was that the MCAS returns trim to previous/ past position if the trigger event/condition no longer exists after the initial nose down trim command. So you can understand the logic, as the MCAS was only to reduce the nose up pitch moment as AoA approached stall value.
It was obvious with Lion 610 that the abnormal AoA was still present every time the 5 seconds elapsed. And the fact that every time the pilot beeped the trim switch that the uncommanded nose down disappeared.
[added] The sad part of the story is that the same AoA sensor MCAS was using was the one making the stick shake. And it may be that the left/right logic for the flight director and other stuff has a human factor deficiency as well
Gums sends...