The guy on this link details 3 common problems that they have, and gives a simple fix for the missing resistor connection.
However, an new issue has been found.
Some users have received sensors with the TL555I flipped 180 degrees.The sensor is, of course, defective because of this.
![Image](https://ae01.alicdn.com/kf/A828a83810be54540a74afc593db25b77n.jpeg_.webp)
I hope this helps!