My normal routine is to hit the feed (30 min pause) button on my return pump and skimmer when I feed my fish. Even the water draining down from my overflow will raise the sump level by an inch, so I have to either unplug the ATK every time I feed or reset it once the system starts up again. If my protein skimmer shuts off because the container is full, the water level in the sump rises about ⅜" - just enough to trigger the backup sensor.
Another issue I've run into is that the occasional snail or other factor that may temporarily lower the flow through the return pipes can cause small variations in the level of the return chamber. Normally these aren't a big deal, but with the ATK it has been enough to trigger the over fill alarm.