I have worked on trucks for many years but never seen this! My 99 F250 doors work normal most of the time. The key fob thingy locks and unlocks perfectly, doors unlock with key no prob. But! Intermittently neither will unlock! Cant even turn the key in the cylinder of either door nor will the fob make a sound at all in door. After working with key maybe 5 min, it unlocks with key, after that fob and keys work perfect again. I have two fobs and two keys. When it does it nothing will unlock door, any ideas?