Yes my OH had a pair that leaked on one foot. I rang them and they replaced them with a new pair within two days. The new pair didn't leak throughout the whole of last winter so overall pleased with the service and the replacement boots.
I have rung them, they want me to send them back so they can check themselves - as they "haven't encountered this problem before"!
Thing is this will be the 2nd pair I've had to return, (these took months to arrive!)
I had some but without the zip and mine were actually amazing, I kill boots. My Ariats lasted 6 months and several other expensive pairs even less but I actually wore the sole out on my Kinpurnies and they were still water tight so I'd say its not the norm and would as suggested contact them