I brew double batches and keg . When I put a keg in keezer all is good and great beer flows. It seems the second keg that sits on a second co2 system in spare bedroom is becoming oxidized. It has happened a few times and always the second keg. These kegs can sit for some time , even a few months, but under pressure in a keg. I am miffed on this one. O2 getting in somewhere I assume. The degree of oxidation is lower but I notice it and smell it in a glass. All my beers are closed transferred . Any ideas?