Albert and James run away from home and get stuck in a severe thunderstorm. They spend the night at a nice old gentleman's home to stay dry. When they arrive home the next morning at first light, there is no sign that it rained all night. Everything is bone dry.
When the family is at the Mercantile for the shoes, a Maid-Rite washboard is in the windows. The series was set in the late 1800s, yet Maid-Rite did not begin until 1926.
If all those people crowded into the house is a major problem for the family, why doesn't Charles simply put an addition on to it? He owns the lumber mill, and has carpentry skills, so it shouldn't be an issue.
It is never explained why the Ingalls family never uses the sodhouse anymore. It was home to dozens of others previously.