Cracks pick the corners because that is where the stress goes.

Cracks in Door Frames, Ceilings, and Corners: diagnosed and explained.

Cracks at door frames, ceiling lines, and wall corners mark the exact points where a shifting foundation concentrates stress. Houses do not crack randomly: when a structure is forced to flex, the stress routes around every interruption in the walls and piles up at the geometry changes: the corners of door and window openings, the joints where walls meet ceilings, and the corners where walls meet each other. That is why the same three locations show up in almost every settling home. A crack angling up from a door frame corner means that opening is racking as the wall tilts. A crack running along the wall and ceiling joint means the wall and the ceiling structure are moving at different rates. A crack down a wall corner means two walls with different support conditions are separating. Any one of these can also have an innocent cause, from lumber shrinkage in a newer home to a poorly taped drywall joint, and the innocent versions are stable hairlines that never change. The structural versions cluster, grow, and travel together, typically with a floor that slopes toward the same area and doors that have started sticking. In Southern California, Arizona, and Nevada, the engine underneath is usually expansive clay swelling through the wet months and shrinking through the dry ones, moving the foundation unevenly a little more each cycle so the stress points never get to heal.

For the repair side of this, the foundation repair solutions page lists every method Dalinghaus installs, including the ones that fix problems other than cracks in door frames, ceilings, and corners.