It means exactly what it says - bad connections - and the solution is to make good connections.
To elaborate: returning 127 means Arduino cannot see the sensor, and therefore thinks it is not present. If it is there but improperly connected, it means the same thing to Arduino - no sensor, hence -127.
They may have the same problem where the connections per se are actually kosher, but you are using cheapo cable, and the end result is the same. It could be that the cable is simply too long, but normal practice should be good for about 10m.