The only reason for this fault now manifesting itself can only be due to either a design fault or the incorrect choice of material, or a combination of both.
What other reasons could there be?
A bad batch of tubing, a different welder, human error, problems in the chassis coating process, mishandling of the chassis during assembly, pothole damage etc.
I'm not saying it isn't a design fault but as at present its manifesting itself only on a subset of cars in a particular date range then it's wrong to simply state design fault.
What is correct is that MMC have reacted quickly to design and install a mod to affected cars.
Now the problem is known about it's an easy area of the car for owners/dealers to check.
