I think the "downstroke blackout" is a lack of focus. When we lose focus we lose the preparation and we lose our rythem.
When this happens i imagine a drill i do at the range, but on the course:
When i am really working on my accuracy and ball striking i put two clubs down on either side of the ball and leave very little room, think 1". This drill has done wonders for my ballstriking and can create quite a crowd around you too when you are striking them well.
Anyway, imagine those two clubs on either side of your ball when you're on the course, PICTURE THEM THERE.