The drop detection was on and the camera will not focus completely- how do I get it refocus?

you have to keep your finger half pressed down or it will always refocus and also do a new light reading.if you keep your finger half way down and reposition it should stay locked

Could this be failing batteries? If you don't use the flash and keep the camera on the same subject so it doesn't need to refocus between shots, what happens then?

it is not a problem it also occurs here in india it is a natural thing for a new restart. it will detect the aprature shutter speed and auto focus

It sounds like it's simply auto-focusing. When you're filming and the camera auto-focus sensor detects a new focus object, it will attempt to refocus on the new object. In lower light situations, this may take longer for the sensor to read the new object. The only way to resolve this is to turn auto-focus off (if your camera allows it). If your subject area remains in the same plane of focus, you shouldn't have any focus issues. If it changes, however, you will have to manually refocus to the new plane, just as you would with a manual camera.

Hope this helps!

I'm thinking this is a depth of field problem. The lens iris will be opening up fully at night reducing the depth of field the set focus point will then not be in the focus range.
Possible Solutions:
Use a ND filter in front of the camera during the day and refocus the camera this will ensure you are in the focus with the lens iris fully open. The WZ16 has an IR corrected lens so you should not be seeing focus shift problems.
Focus the camera at night.
Ian Crosby Product Marketing Manger EMEA Bosch Security Systems >>> For the WZ series amongst others

I have the same problem with the same camera. I believe the problem can be solved by turning the knob to MOVIE mode, then push the menu button. When the menu screen pops up. Go to the "camera" tab. It should be the first tab to your far left.

Once you are at this tab, scroll to the very first option which should be the AF FRAME option (Auto Focus Frame). Select "CENTER" for the Auto Focus and do not select "face detect." I think when it is in face detect mode it is sometimes searching for the persons face. If you just leave it in CENTER mode, then it just fixes itself in the center. This is what I am going to try. I think it should work.

Hope that helps.
Peace

The wheel that holds the lens is broken - its thread is gone. Disassemble the camera - don't broke the wires from the data cable, start the pc and adjust the camera to be focused on the position you will use it normally, use a drop of glue to fix the lens in place and put it all back together. 

If you aren't planning on zooming in or out, you can lock the AutoFocus by:
- first assign the shortcut key to the AFL (Auto Focus Lock) setting (by going to Menu, then "Set Shortcut button") - then while filming, press the shortcut key (which you have assigned to the AFL setting) and the focus will adjust and unlock (the AF will unlock when you press any other button). - each press of the shortcut key will adjust and lock the focus

Check the rear optic on your lens. Then may be dust or debris preventing the focus to lock on your subject.

http://panasoniclostfocus.blogspot.com/
Common problem with Panasonic cameras. Read comments from other owners at the above blog and send a description to me at the blog. I will post it. Also check 3CCD USER.COM