The key goes into the lock cylinder, the lock cylinder slides into the PassLock Module and the module/cylinder, as a unit slides into the ignition switch.....the ignition switch has nothing to do with retaining the key......
The problem is either the lock cylinder or PassLock module.....it would have to be removed and it's operation checked.......There is a special procedure for removing this.......a manual or online subscription would show this...
Basically, you turn the key to the "on" position and you depress a tab, and the key/cylinder/module slide right out....there are several ways of getting to this tab.......manual shows this.....