Sound's like you are describing spalling, where the action of the weather causes the face of the brick to crumble and break away. I'm only a novice diyer, but would think that you need to remove the whole brick(s) and replace. If there is any other way I would love to know, as I have the same problem with a garden wall.
I've got this problem on my walls. The bricks are soft, and the brickie would insist on putting cement in the mix. If he'd used lime mortar instead, the joints might have worn away, but the bricks would be ok. This is a problem in many places,
If they are the Fletton or LBC type bricks, they seem to have their problems, but I don't know how they would fare in a lime mortar wall.
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