Worrying brickwork discovery

[DigiGran]

Undertaking a few tasks on my 76-year-old house, built of double skin ironstone brick. I've noticed that where I have encountered the brickwork of the nner skin, or the outer skin beneath the pebbledash, the mortar is...er...sand.
Or what was mortar has turned into sandy stuff.
I am minded to just leave this alone and hope.
What would your reactions be - and does anyone know if this is due to some kind of weathering (how?) or long ago bad work?
TIA

 

[blup]

Brick walls are held up by their own self weight, so soft sandy mortar that has dried out shouldn’t be anything to worry about imo but I’m not a brickie. If the render is allowing the wall to breathe and no damp leave as it is.