This is probably the most common question we see, and that we have seen over the past 12+ years. During fermentation, some of the carbon dioxide created gets dissolved in the liquid. After fermentation there is still some CO2 trapped, and slowly escaping ,just like an open can of soda, just not to that degree,. This will cause a small amount of activity through the airlock, making you think that there is still activity, where in fact fermentation is complete.

The final gravity is also in line with a grain mash. You will be left with some un-fermentable longer chained sugars in your wash. These lend body to a beer, but for your purposes they have no real effect. They do cause a finished gravity above 1.000, which can make one think that fermentation did not complete.