If you have horizontal cracking every few courses of bricks then the likely cause of the problem is wall tie failure. If left uninspected and diagnosed then eventually this can lead to failure of the structure.

The only way to 100% confirm the situation is to get a camera into the cavity and inspect the wall ties to ascertain thier condition. 

Tennyson Surveying will inspect a number of sites within the wall that appear to be at risk and then give photographic evidence of the situation in hand.