I have a mixed set of irons, 4,5&6 are Hotmetal others are forged. The 5 is by far the worst but I can see some evidence of this on the 4 too.
I am hacked off, it is true. I would welcome advice on how to contact Mizuno but unfortunately the Pro that I bought through is no longer in business and others with Mizuno accounts would, understandably, be reticent of pushing Mizuno on my behalf as they don't owe me anything and wouldn't want to upset Mizuno. That leaves me out in the cold!
If anyone from Mizuno monitors this forum - I would welcome a discussion on this.