One tip for retaining wall repair is to wet existing joints with water before applying new mortar to repair cracked joints, so that it does not crack when dry. When repairing cracked stones, all debris must be cleaned away to allow the epoxy-based filler to adhere to the surface.
When filling a cracked stone with adhesive, fill the crack from one end to the other as seamlessly as possible. Before repairs, clean the retaining wall using mild liquid soap or stone and masonry cleaner, using warm water and a stiff scrub brush. If the wall is buckling, it has to be demolished and replaced, including placing new footing. New mortar has to dry for at least seven day before it is cleaned.