Konstantin has it right on this one guys: Inspect for stuck function keys very carefully and don't waste your time fiddling with software, drivers, batteries, replacement keyboards, and operating system re-installs (yes, I sheepishly admit I did that the
first time I had the problem after all support's suggestions had failed, and they told me reimaging was the only way to go. .
People understandably think all kinds of things fix because it suddenly seems fixed, especially after they've been flipping the keyboard over to fiddle with the battery compartment. I think it's fooled them. It wasn't the battery work that fixed it, it's
just that in flipping the keyboard over, they likely "accidentally" fixed it by brushing their hands sideways along the function keys. The third time this happened to me was on booting up after I'd wiped the keyboard with a screen wiping cloth to remove skin
oil. I peered at my keys for a good couple of minutes and all seemed fine, until I finally noticed the right side of F3 was riding just a few millimeters low. Hard to judge that on a curved surface. A very gentle nudge of that key to the left made it pop up,
almost imperceptibly, but: problem solved.