I have the H5 and recently began to have problems with the focus lock. There have been many posts on the internet concerning the H1 and H2 shutter buttons falling off the camera, etc. One or two users posted pictures of the cameras or repairs they had attempted. Mine didn't fly apart, and on the Sony parts list, the 'release assembly' is a different part number for the H5 so I believe it is a little different design from the H1 and H2. After taking mine apart, I can see that the H5 is a little different from the H2. The focus lock just stopped working altogether. No amount of desperate 'default' settings, new batteries, etc would help.
When I opened it up, (darn I wish I had taken some pics), there was a small ribbon cable of sorts mounted on a moveable piece. When the toothpick-sized plunger or shaft from the button contacted the ribbon cable, a conductive piece on top would connect the two traces, causing the focus lock to activate. Further force would cause the whole assembly to hinge down a bit, setting off the shutter release switch located directly underneath.
The conductive disk on the flex circuit had a depression in it from the plunger of the shutter release button. I honestly believe that it was simply form pressing the shutter button too hard or too many times. I have taken literally thousands of pictures with this camera over the past ten months. I had just been taking some pictures of dragonflies in flight using the burst feature. After a burst of pics it takes the camera longer to process and store them than usual. I would press the shutter, when nothing happened, the natural instinct is to press harder for a second, until it dawns on you what is going on. I'm accustomed to the best from Nikon, Canaon, Minolta and Pentax, with film, where a press on any button means something is going to happen NOW.
Anyway, it appears that I repaired mine at least for now by lifting the dark circular piece of conductive material and repositioning it a bit on the flex circuit. It is held in place with adhesive. I used a pair of needle tweezers, and I was very, very careful. I have the hands of surgeon, and a helluva good pair of reading glasses and a magnifier. So if you're doing this yourself, do it during the day, and be very careful.
I considered sending it back to Sony, who uses a camera repair facility in New Jersey, but after reading horror stories about peoples experiences with them, I am a bit leery. If my fix turns out to be short-lived, I suppose I will not have any choice, as the warranty runs out in a couple months.
The purpose of all this is to let others know, to press your shutter button gingerly, as after a close-up look at the insides, I can tell you it was not designed for a lifetime of use. It looks more like they expect you to use it on family occasions, for a few years, then abandon it for a newer model.