Bread is not rising

The problem

After ten years of baking bread, I have a new problem with my bread rising—it seems to fall when baking in the oven.

I've used the recipe below with good results, yielding nice 1–1/2 lb loaves with good flavor and texture. I've varied little from this process, but my last two bakings have left me puzzled.

The first and second restings have met expectations—a good rise and development of yeast smell. The rested loaves did not quite meet expectations but at least doubled in size. After baking, however, the loaves shrank somewhat and came out barely bigger than what I placed in the pans.

I could really use some help here. My family loves my bread, and I do too—until now.

Things I've tried/considered

My method has not changed, but my brand of bread flour has due to stock availability during the COVID-19 lockdown:

• Previously I exclusively used King Arthur Bread Flour.
• For my last two bakes, the only available flour was Ceresota Unbleached All Purpose Flour.

My yeast is an instant yeast I buy by the pound from Gordon's Food Services and is apparently the same as sold in King Arthur's catalog. All other ingredients are off-the-shelf brands and have not changed.

Thinking the yeast may be old, I replaced it with 4 packets of ordinary instant-rise yeast this last time. The same thing happened: all appeared well, smelled well, felt well during kneading, but the loaves failed to rise and even shrank somewhat in the baking.

I tested the oven and found nothing wrong or out-of-order. The only major change was the flour, and I find it difficult to accept that minor difference in the flours would produce such a change. All ingredients are weighed.

Bread recipe

Ingredients

• 100g granulated sugar
• 70g brown sugar
• 85g molasses
• 30g butter
• 150g rolled oats
• 1 cup near-boiling water
• 3 cups room-temperature water
• 210g whole wheat (Bob's Red Mill or King Arthur)
• 24g yeast (4 packets)
• 1150g bread flour (see note above on substitution)
• 90g wheat germ
• 10g salt

Method

1. Mix sugar, brown sugar, molasses, butter and oatmeal with the near-boiling water (to partially cook the oatmeal) in a stand mixer for 5 minutes.
2. Cool the mix with 2 cups room-temperature water, bringing the mix to skin temperature.
3. Add whole wheat and yeast.
4. Incorporate the bread flour, wheat germ, 1 cup room-temperature water and salt, mixing until the dough begins
   to pull away and form a ball. (I use the wheat germ for higher gluten,
   believing that this reduces the crumbling of the finished bread.)
5. Remove the dough and let it rest, covered, about 20 minutes.
6. Hand knead the dough for about another five minutes, cover it and let it rest about 45 minutes in a protected spot—usually the oven,
   warmed depending upon the season and kitchen conditions. (I pre-warm
   the oven by setting the temperature at 190F and turning it on for 1
   minute.) The four pottery loaf pans I use sit in the oven with the
   rising dough.
7. When the resting dough has doubled or more, remove it from the oven, knead it for not more than 3 minutes and return it to the oven
   for another 45-minute rest.
8. After the dough has doubled in size, remove it from the oven and portion it into four equally sized loaves, place them in the pans and
   return them to the oven for another rest until they double, about
   30-40 minutes, covered with a towel.
9. If satisfied with the rise, remove the towel and set the oven for 365℉ or 375℉ and let the oven achieve temperature. The whole baking
   process from cold to completion is usually 33–37 minutes. The bread
   will rise further until the loaves are three times the size when I
   first introduced them into the pans.
10. When the loaves are done and have achieved an internal temperature of 195℉, remove them from the oven, place them on a cooling rack ( I
    usually leave them on their sides) and cover them snugly for cooling.