NZBGet is an advanced usenet downloader that has a wide array of options to customize your downloading experience. Some usenet servers propagate more slowly than others meaning that you can be downloading a movie or tv show before it is on your provider's servers which can result in a failed download. To workaround slow usenet propagation with nzbet there is a special feature.
Workaround Slow Usenet Propagation with NZBGet
Open up your nzbget installation through the webui http://ip.address:6789 default username: nzbget, password: tegbzn6789
Click Settings at the top then Download Queue on the left. Go down to Propagation delay and choose a number in minutes, 30 should suffice but if you are noticing more failed downloads you can increase it to 45 or 60.
Scroll down and click Save All Changes
You will get a message to Reload NZBget afterwards. Click Reload.
With propagation delay enabled nzbget will keep the nzb in the download queue and wait 30 minutes (or whatever number you choose) before it attempts to start downloading.