Well, for what’s it worth, here’s what I found out. The weekend after I had all those problems with baking, I pulled out some of that problem dough from the freezer, let it thaw and added a few more tablespoons of flour. Everything baked up perfectly.
I then tried my spritz recipe, which had also been spreading when baked the week before. I made it as I always do and did a test batch. They spread. I again added a touch more flour, and the rest of the dough behaved beautifully.
It was at this point that my husband told me that when he went grocery shopping for baking supplies the store was out of King Arthur Flour, so he bought another brand—I think it was either Gold Medal or Pillsbury. Because we store all our baking supplies in clear plastic tubs, I didn’t realize that the brand was different than usual. It was all unbleached, all-purpose, but I wonder if gluten/protein contents could vary enough to make a difference?
In the future, I think I will do as Cathy suggests and bake a test cookie when I am doing big batches.