There's a whole thread on this. We call ourselves the bubble club. Exclusive? maybe. I started a case with Ford to solve the problem. Gave them pictures. Just picked it up from the last recall/battery replacement. After 2 weeks of back and forth and no answers they told me pictures wernt good enough to solve the riddle and I would have to leave my truck with the service department for an answer after they run diagnostics. Needless to say I said thanks but no thanks. Truck runs fine. I don't want to risk them fowling up my truck. I've been less than pleased with my local service department and Ford support.
I noticed the bubble for the first time yesterday, shortly after I started the engine. Went away pretty quickly. Clearly a software bug which will eventually go away.