My seven year old told the neighborhood our garage code so I changed it per instructions - press the learn button, led comes on for 30 seconds, enter new code, hold enter until light blinks. Problem is, now both the old and the new code work. I cannot find anything about this in searches. I don't have the model number at the moment but the house was built in 2004 and it's original to the house. Any help is appreciated!! Thanks!