Smart Key Question

[nyko46]

My 2009 Mercedes Bluetec original Smart Key is going bad and I don't know the reason.
As the car was bought in a small dealer from another owner it came with only one key I decided stop by on a Mercedes dealer and ask to make a new one using the VIN of the car. Dealer made one functioning perfectly. The same dealer commented with me that my original key is "almost gone" he said.
Days latter I questioned myself : "how come a key that is not a mechanical key can go bad? How come an electronic key can slowly go bad? "
I then change batteries for a fresh battery but it still with the same issues.
This is what happen: when inserting the key on the ignition it take a while to the car recognize that the key was inserted. When open the doors from outside I need to press the unlock buttons twice in order to get the doors unlocked and the same occurs to lock the doors, I need to press it twice. Open the trunk with the key is even more complicated when using the this Smart Key. The one just made on a dealer works at the first touch and the car recognize the key instantaneously.
This old key sometime stay with the little red light continuously on and then I need to open the key and remove the battery to "reset" to get it working again.
Any idea why it occurs or if it is normal to occurs with old electronic keys?
Thanks.