There’s a switch that is activated by a rod in the steering column. That switch gets gummed up and can break. It has a rotary contact in it that can also make for some odd intermittent action.
The switch is actually pretty accessible (not easy, but accessible, probably only a few cuss words) by taking the covers off the lower steering column. I don’t have a photo, but they are out there.
Don’t make the mistake of thinking it’s in the stalk or the column itself unless you know the mechanical linkage is broken. If you are still getting a click when you pull the stalk back, it’s probably the switch (though you should double check the linkage given your truck seems to have lost all switching actions but is stuck on high beams). The switch is way down on the column near or just under the dash.
