Sailing boot soles have gone hard and now slip in the dry. Is there a cure?

[ex-Gladys]

I thought I was buying a premium product but my Dubarry's boots went slippy after around 3 years of little use,
Dubarry could only suggest that I sandpaper the bottoms. I don't think the newer boots can be resoled by Dubarry like the older ones.
I went to a local shoe repairers and she stuck a new sole over the old one but they are still not as grippy as I would like.

I won't be buying anything else from Dubarry and certainly would not recommend them after my experience of them.

Strange, I have a pair of Dubarry boots that I've had for 7 years (but only wear 2-3 times a year), and 2 pairs of deck shoes, both of which were bought seriously cheaply, and stick like nothing else - even the old slip on ones that are almost bald on the ball of the foot. I have tried other makes, but have had no issue of hardening at all... My old Musto ankle deck boots... that's another question...