there are probly other areas blown and failing higher up.any signs of internal damp?
looks like repairs were tried in the past but the external exposure,perhaps movement cracks in the background, and the wrong kind of non masonry paint have allowed moisture to get behind the surface.
the string course ledge might be flashed but it looks well flat so it could be ponding.
youl probly find its cheaper in the long run to hack the lot off and redo maybe in a more modern render?
