Dirt around ignition switch or aerial loose?

Do you have a lot of keys on the keyring?

There's a small aerial around the ignition switch which reads the immo chip in the key. If it's loose or badly fitted, or if there is a lot of dirt around the switch, it might cause this problem.

I asked about the keyring because other immo keys can cause read problems, and too much weight can pull the ignition key away from the aerial.