Leaking water heater gas valves.

I am not an inspector but a contractor.
Am having an argument with A.O. smith Corp. about their water heater gas valves on their GCVL model water heaters. I recently installed this water heater for a customer who later complained of smelling l.p. gas. Upon inspection I finally found the gas valve leaking behind the plastic cover on the valve body. Subsequent and consecutive replacements of this model valve produced the same problem. The same leak in the same place. Three new gas valves later and finally, at the customer’s request, an eventual different brand of water heater, A.O. Smith refuses to acknowledge their liability and I get nothing but corporate blow-off on trying to be reimbursed for nearly 7 hours of labor, travel and efforts remedying the problem. But that is another issue. The leak is very small and probably not threatening as it is, nevertheless it’s enough to stink and not something a customer wants in a new water heater. Who can blame them? I’m guessing if there were four of them off from one shelf, there are probably 400 out there somewhere.
The valve is a self diagnostic valve and the A. O. Smith # is 9007890005.
I would like any information I can get from anyone who has run into or runs into this valve and finds a like problem.
I’ve attempted to attach a photo of it but am not familiar enough with this site to do so apparently. Any help would be appreciated and I can be reached at : jeffraymond@live.com Thanks!