97 Bravada - Can't pull key out of ignition

[PepperNE]

About a year ago, I had the dealer put in a new ignition switch and everything worked fine. Now, a year later, when I'm turning off the vehicle, I push the button on the gearshift lever and put the gearshift lever into Park and and hold the brake down. Then, while still holding the brake down, I turn the ignition key to the OFF position. At times, I will hear a click in the steering column which tells me that the ignition switch is in the lock position and the key can come out. But, most of the time, it doesn't want to click into the lock position and I can't pull the key out of the ignition switch. Can you give me any advice as to what is causing this and what I can do to fix it?