Nissan Micra does not stop

Hello.
We have a 1998 Nissan Micra 1.5D GX.
A few weeks ago, when we removed the ignition key, the radio would stay on. This happened 5 or 6 times.
It stopped.
Now, though not always, the radio stays on when we remove the key (turn it off), but the engine also stays running.
I've started searching online, and people say it's common for the fuel cutoff solenoid to malfunction, but looking at the wiring diagrams, I think it's more likely the ignition switch contacts (OFF-ACC-ST).
I'd like to know your opinion before doing anything.
Thank you very much.

I'm leaning towards the ignition control unit behind the key cylinder; it's responsible for both starting and stopping the engine. It's not an expensive part and it's easy to replace, although you should test it with a test light first to see what happens.

Hi, I don't understand the part about the lamp.
Could you explain that test to me?
Thanks.

if it's the ignition cylinder

One more thing, to replace it, will it be necessary to remove the steering wheel?
I was watching a YouTube video of a replacement procedure, and it involves removing the steering wheel, the ignition switch, and everything else.
Thanks.