This is because of one of the features in the Apple Watch that was designed to make calling 911 easier. This involves a long-press on the side button which would allow someone to call for help discreetly and quietly, but for some, this button might have accidentally been pressed while they were sleeping, leading to unnecessary 911 calls and a strain on resources.
This seems to be happening quite a bit particularly in Kansas. According to the Overland Park’s 911 call center, they receive about 250 calls per hour, which is already quite considerable, so throwing in unwanted and false 911 calls into the mix is something that the center says that they could do without.
The good news is that the long-press feature can be disabled which should help reduce the number of false calls, but this is something that users will need to manually disable themselves. Alternatively, buying a case for the Apple Watch could also help to reduce the possibility of an accidental press.