I've been having issues with this as well. I find that with an Olympus 17mm it takes forever to change focus even with tracking. In most of my shots on a stabilizer with moving subjects, it stays focused on the background no matter how close and how much area of the image the subject takes up.
Curious if the Panasonic lenses are better at this than third party lenses?
Cheers,
pete
I've found that the Oly 45 auto focuses faster than my Lumix 14mm.