Blown render or something else?

[Itlookslikerain]

We live in a Victorian terraced house and our neighbour has come over saying the render has blown near the coping stones right at the top, in between our houses. Turns out they’ve had terrible damp in the kitchen for 5 years but only mentioned anything a few months ago. He came over today saying kitchen electric sockets have flooded with a couple of the wires eroded away and has such bad damp they can no longer use 2 of the kitchen cupboards.
He had a loft extension done 2 years ago and said he’s had 2 contractors come over and they’ve both said it’s our house- neither have quoted to repair or came to speak to us. We’ve had 1 renderer come over to repair another area of our house, and he said the area in question looked fine.
We had no damp or water damage anywhere, we’ve checked throughout Inc the loft. Could this be something else on their side to cause such excessive water damage? It’s odd to be on our side and have not a drop of damage.

 

[Notch7]

Is this a parapet wall on a pitched roof between their roof and yours?

or a parapet wall on a single storey flat roof

its hard to visualise

 

[Itlookslikerain]

It is a parapet wall between their pitched roof and ours

 

[^woody^]

I can't imagine how any blown tender one side of the boundary could cause damp to a neighbouring property.

 

[Itlookslikerain]

It’s the amount of damage that’s been done- to travel 2 floors and see no damage and suddenly there’s loads seems baffling. Especially when we’ve had an incredibly dry summer.
If it turns out to be my property I’ll happily repair it but I don’t want to spend £1000 ‘just in case’, especially when they haven’t had the damp investigated or any trace and access on the mass water in the electric sockets.