I updated the code on my github page. The new code hasn't been tested yet but I will explain what I believe was the problem and what I did to solve it.
I believe there is a problem when the millis() function overflows. This happens every 49.7 which corresponds to when the system went online and when it stopped reporting to wunderground.com. When I was researching possible alternatives for regularly timed operations I came across elapsedMillis & elapsedMicros. It is a standard function when using Teensy hardware and available as a library for Arduino.
I expect to upload the new firmware around Christmas.
Hopefully someone will adjust the camera directed to Picton before Christmas. A possum climbed on it on 2AM on December 1st. You can see the image shift on the time lapse on wunderground.com.
George Timmermans, Research Toolmaker, Software Engineer and Tinkerer