Camera archive, missing images

Can someone explain what is wrong with my camera settings (Vera 3 1.5.408, timezoon +2)?

On settings tab I have set: For archive purposes, take a picture from the camera every 2 hour, number of days to keep 7. When I check archived images there should be 12 (11) images but there are always 12 hour gap (images missing).

Archived images (yesterday 07:11.2012): 01:04:47, 03:04:47, 05:04:47, 07:04:47, 17:04:47, 19:04:47, 21:04:47 and 23:04:47. Missing images 09:04:47, 11:04:47, 13:04:47, 15:04:47.

This happens every day. If I change the interval it seems that number of images is changed but there is always that 12 hour gap between archived images in the middle of the day.