F355 central locking gremlin

While driving my car last week, I activated the central locking switch. When I wanted to open my door, it didn't open so I activated the unlock button. Since then, my central door locks go up and down. In the beginning it was quite funny, but now it's rather annoying. I shut off the battery for a while, but this didn't help.
My car hasn't got an OEM alarm, so it can't be the cause.

Any ideas how this could be solved? I didn't yet check my fusebox, perhpas there is a melted fuse. Thanks for your help,

David

 

Today I took my car out for a ride. It was a great day, sunshine, howling Capristo but after about 10km, the engine suddenly died. I tried to restart it, but after half a sudden it shut down again. I disconnected the battery hoping that the system would reset, but no avail.
It seems to be related to the alarm, but it's not an original alarm I'm afraid. It's a 96 Spider, which originally came from Germany. Instead of the alarm, it comes with a small key you need to insert above the ignition key in order to start.

Any ideas?

Many thanks,

David