On my daughter's 4wd blazer, the vehicle will engage 4L and 4H on it's own on 1998 Chevrolet Blazer

this happens without pushing the 4wd buttons and seems to happen after she has driven a short distance then parks for a short time. It takes several tries to get the vehicle back into 2wd. Simply pushing the button does not work.

Is it actually going into 4x4 or just the light says so? Is front axle engaged? You stated it goes into 4 lo also, are you sure about that? Should not be any trouble to tell if it is. While driving do you hear any noise like the front axle is trying to engage? I own a 2000, same setup and may be able to help with answers. Could be a simple fix. But before i go on, need more info.!