Question about steering lock system on tricycles

[Anna]

We recently bought a Berchet tricycle for my two sons. It has the steering lock system which I thought was going to be really helpful since neither one can pedal yet. However, it doesn't lock the front wheel completely into place. They can move the wheel about a half inch in either direction. That is enough to make the tricycle go off to one side when we push. Is that normal for the steering lock? Or, did we get a defective tricycle?

Thanks!
Anna