You may have a weak pedal return spring. If you hit a pot hole or big enough bump your pedal will move and make contact with the brake switch. I used to battle this constantly on our International flat beds we own. It could also be that the fuse is lose in the holder and is vibrating and making intermitent contact. This is a pretty easy fix because all you have to do is tweak the legs on the fuse to tighten it up. Hope this helps

 

Add any led turn or brake lights recently? That will mess with your cruise if you don't add load balancers...

 

Did this get resolved? I am having the same trouble with my 2004 lariat as well..