Comment by BeniBoy

My father encountered one of these voodoo issues once. He works in satellite images processing. Basically uses Spot data to analyse ground vegetation coverage.

One day while processing a batch, he noticed one parcel was giving the most awkward results. Totally different that anything he ever saw. This bug troubled him for almost a week, he couldn't figure out wether the satellite malfunctioned or if something was amiss in his calculation. Then it clicked, and a quick internet search confirmed his intuition. The satellite took the picture right in the middle of a solar eclipse!