The shaft may have been burred which could have cut the seal. Do you recall fucking w/the cylinder prior to install? Did you at all place any kind of grip from a wrench on there to hold it still while you did something? My KYB 4-Ways have been in place now since 2001 and they are great. So 1 of 2 things. You either did something wrong when installing or KYB had a factory defect (it happens) which they will replace. Just act like you don't know what happened when asking for a replacement. Don't give any indication it may have been your fault which may cause them to void the warranty.