My nanoleaf shapes will sometimes turn on or off without any interaction from me. It seems like, when it happens, the shape switches from its intended setting to the reverse (off -> on, or on -> off) and it starts to show as "disconnected" in the app. It will generally go back to the intended setting after 30 - 60s, but not always. Generally using the physical on / off button will reverse it immediately, but you can't issue the shape orders from the app.
I have two shapes and one of them seems to do it more often than the other, but it might be that I just notice it more because it is in my sight line. This bug is particularly annoying at night as shapes will come on at full brightness in the middle of the night and wake me up. The most effective solution I've found is to simply unplug a shape before going to sleep.