Rain. Lots of it.
More demolition, discovery and excavation. In spite of our best effort early on to investigate the existing conditions of the house, we discovered, besides many former colonies of termites, that the foundations were in really poor shape where we needed them not to be. We resolved by developing a plan that simply abandons the old footings in many areas and focusing targeted replacement in the critical areas.
Demolition has been completed and most of the debris has been cleaned out. Typical of older homes is the discovery of hidden damage and "unusual" framing. We found termite and dry-rot damage in several locations. Fortunately most are in areas that are being rebuilt.