Footing trench not compacted. Foundations are critical and nearly impossible to replace. They should be numerous and well-marked, at each interior floor level, thresholds, and outside against the building. Foundations take longer than you think, especially rock walls. Beginning too late in the season.
Cob needs time and dry weather to dry.
Wet walls can be damaged by frost. Wet straw in them may putrefy during the winter. Wet earthen floors dry extra slowly. Thin walls too straight. Cob needs lateral buttressing, either by building thick, building curved, adjoining walls or structural buttresses.