Render cracks suck in water. When it is raining, it is common to see da dribble of rainwater running down a rendered wall until it meets a crack, then being drawn in, disappearing within to cause ingress. Sometime only the external wall is affected, causing heat loss inreasing the risk of condensation. Sometimes the water causes penetrating damp and occasionally timbers become damp, risking rot.
Watch this space!
Mode details are being uploaded regularly, towards the end of every month.