Belleair

I've recently had problems locking my CLA45 AMG ! She's only 2 months old firstly pop it in park , press the turn of engine button . I usually can tell if my radio doesn't turn of when I open my door , I know it won't lock. So I have to manually turn the radio of , open the door and have to use my key to lock the door manually . I've taken it to Mercedes service, they've ran diagnostic and changed the batteries in both fobs , and it's still happening ! This happens randomly and won't happen all the time. Usually it happens when I have my hands full and I can't use my fob to open then car and have to manually remove the key from the fob . any help would be appreciated.