The advforecast2.php script checks to see if it needs to update based on the age of the forecast.txt cache file. If the file is older than 30 minutes (1800secs), then it will load from the URL you specified (for the point-printable forecast from weather.gov) and save the returned page for future use in forecast.txt.
It then goes on to process that returned page for icons and text. When the forecast.weather.gov site is providing point-printable forecasts, all the icons and temps and text look fine. If they were having an issue and substituted a Zone forecast for your point-printable one, then the script changes gears and parses the text forecast returned for key words to indicate which icons to use and the approximate temperature range forecasted in the Zone forecast. When the point-printable forecast is available again, the script will load it when the cache file age is > 30 minutes.
You can use the ?force=1 on the wxforecast.php page to get it to reload the cache directly.
So.. long winded explanation, now the question:
What is it you are seeing when you suspect the script is not reloading as you expect it to?
Do you have a screen-capture of what it looks like when that happens?