Cords sawing through plastic?

Velux Duo blind cords cutting plastic?!
I contacted Velux only to be told blinds were out of warranty! I told them this would happen given the make up of the blinds, even if the warranty was five or ten years let alone two years. The company fail to realise or do not want to admit to the problem. I worked out a simple workaround that stop the cords sawing through the plastic

Les.