I have found that random disconnects can happen if your FP2 is connected at 5 GHz, and your router is configured to automatically select a suitable channel. Apparently the FP2 doesn’t like higher channels like 116 through 128, so if the router lands on one of these, it causes the FP2 to lose connection. It may try to reconnect on 2.4 GHz, which is often congested in urban areas, so this might not improve the situation. My solution was to configure the router to use a fixed channel (56 in my case); see my thread here for further details.