https://imgur.com/a/h6NgXct

If those are true sandstone blocks it’s not unusual for it to scale off, especially where water may accumulate.

If they are masonry blocks made to look like sandstone blocks then just have the faux exterior redone.

Either way, I would recommend a good pressure wash and sealant

Is there a water proof membrane on the outside of the wall under the soil keeping moisture away? If not light be time to invest. It's costly but will reduce rising damp into the future.

Assuming there is waterproofing under the asphalta but not 100% sure. The guy who did the renovation before we bought it did some funny things. When the original house was renoed 11 years ago with a 20’ addition put on, the original basement was underpinned and lowered. There is some membrane poking up along the new extension foundation but who knows if he wrapped the old foundation. Knowing some of his other work, I’d say doubtful…

This is in Toronto so the snow bank through the weather piles about 3-4 blocks up. Just not sure why that block would crumble and not others.