I'm sorry to hear of your frustrations with fallen loaves. Bread that falls in the center during baking has likely over-risen. The first suggestion would be to reduce your yeast by 1/2 tsp. If that alone does not bring complete success, you may also reduce the 2nd rise by 5 minutes. We usually start with Rise 2 at 30 minutes, but you can go as low as 20 min. if necessary. (Also, we find that cold winter months bring cooler kitchen temperatures and may require an adjustment in your homemade settings or adding back the 1/2 tsp. omitted yeast, fyi.)
