When these were made in Scotland they were made of tougher material than the ones now made in China.
Now the rubber seems to break down at the point where your big toe connects to the foot, i.e. at the flex point and in a section of the boot that is unfixable.
In decades past I could buy a pair for general gardening and winter use and get 10 years out of them. The soles and heels would wear away before they leaked. But not now.
What sort of rubber are they made of ?, EPDM ??
Andrew