Probably the transponder is not close enough to the antenna being separate to the old key. [as far as I know the transponder on the 3 button unit is part of the circuit board.. ]
You can swap blades also, that is what I do when replacing the plastic button bit. It is a fiddly but not difficult job. You need to remove the small roll pin securing the blade and simply swap blades.
You can swap blades also, that is what I do when replacing the plastic button bit. It is a fiddly but not difficult job. You need to remove the small roll pin securing the blade and simply swap blades.